Data Nugget ‣ Data Nuggets

11.27.17

Is it better to be bigger?

An anole lizard on the island, about to be captured by Aaron.

The activities are as follows:

When Charles Darwin talked about the “struggle for existence” he was making the observation that many individuals in the wild don’t survive long enough to reach adulthood. Many die before they have the chance to reproduce and pass on their genes to the next generation. Darwin also noted that in every species there is variation in physical traits such as size, color, and shape. Is it simply that those who survive to reproduce are lucky, or do these traits affect which individuals have a greater or lesser chance of surviving? Evolutionary biologists often work to see how differences in traits, such as body size, relate to differences in survival among individuals. When differences in traits are related to chances of survival, they are said to be under natural selection.

Brown anole lizards are useful for studies of natural selection because they are abundant in Florida and the Caribbean, easy to catch, and have a short life span. Brown anoles are very small when they hatch out of the egg. Because of their small size, these anole hatchlings are eaten by many different animals, including birds, crabs, other species of anole lizards, and even adult brown anoles! Predators could be a significant force of natural selection on brown anole hatchlings. Juvenile anoles that get eaten by predators will not survive to reproduce. Traits that help young brown anoles avoid predation and reproduce will get passed on to future generations.

Aaron with a baby anole lizard.

Aaron and Robert are scientists who study brown anoles on islands in Northeastern Florida. Along with their colleagues, they visit these islands every 6 to 10 weeks during the summer to survey the populations and measure natural selection in action. Aaron and Robert selected a small island that had a large brown anole population because they were able to find and measure all of the individuals on the island. Aaron observed that in the late summer there were thousands of hatchling lizards on the island, but by the middle of the summer the following year, only a few hundred of those lizards remained alive. He also observed that hatchlings varied greatly in body size and wondered if those differences in size affected the chances that an individual would survive to adulthood. He predicted that smaller hatchlings are more likely to die than larger ones because they are not as fast, and therefore not as likely to escape from predators and face a higher risk of being eaten.

To test this, Aaron and Robert captured hatchlings in July, assigned a unique identification number to each anole, measured their body length, and then released them back onto the island. In October of the same year, they returned to the island to capture and measure all surviving lizards. They calculated the average percent survival for each size category. Aaron predicted longer individuals would have higher survival. This would indicate that there was natural selection for larger body size in hatchlings.

Featured scientists: Aaron Reedy and Robert Cox from the University of Virginia. Co-written by undergraduate researcher Matt Kustra.

Flesch–Kincaid Reading Grade Level = 11.7

Additional teacher resource related to this Data Nugget:

For additional images of Robert and Aaron’s research with anoles in Florida, we have created PowerPoint slides that can be shown in class.
Aaron conducted this research as a graduate student in Robert Cox’s lab. To learn more about anole research, visit the lab’s website. To learn more about Aaron, visit his website.

Once your students have completed this Data Nugget, check out this video on anole size and natural selection from hurricanes!

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11.27.17

Is it dangerous to be a showoff?

A male anole lizard showing his bright dewlap.

The activities are as follows:

Natural selection happens when differences in traits within a population give some individuals a better chance of surviving and reproducing than others. Traits that are beneficial are more likely to be passed on to future generations. However, sometimes a trait may be helpful in one context and harmful in another. For example, some animals communicate with other members of their species through visual displays. These signals can be used to defend territories and attract mates, which helps the animal reproduce. However, these same bright and colorful signals can draw the unwanted attention of predators.

Brown anoles are small lizards that are abundant in Florida and the Caribbean. They have an extendable red and yellow flap of skin on their throat, called a dewlap. To communicate with other brown anoles, they extend their dewlap and move their head and body. Males have particularly large dewlaps, which they often display in territorial defense against other males and during courtship with females. Females have much smaller dewlaps and use them less often.

Aaron with a baby anole lizard.

Aaron is a scientist interested in how natural selection might affect dewlap size in male and female brown anoles. He chose to work with anoles because they are ideal organisms for studies of natural selection; they are abundant, easy to catch, and have short life spans. Aaron wanted to know whether natural selection was acting in different ways for males and females to cause the differences in dewlap size. He thought that a male with a larger dewlap may be more effective at attracting females and passing on his genes to the next generation. However, males with larger, showy dewlaps may catch the eye of more predators and have higher chances of being eaten. Aaron was curious about this tradeoff and how it affected natural selection on dewlap size. For female brown anoles, Aaron thought that this tradeoff would be less important for survival because females have smaller dewlaps and use them less frequently as a signal. In other words, there may not be selection on dewlap size in females.

Using a population of brown anoles on a small island in Florida, Aaron set up a study to determine how dewlap size is related to survival and whether there is a difference between the sexes. He worked with his advisor, Robert, and other members of the lab. They designed a study to track every brown anole on the island and see who survived. In May 2015, they caught the adult lizards on the island and recorded their sex, body length, and dewlap size before releasing them with a unique identification number. Then, the lab returned to the island in October and collected all the adults once again to determine who survived and who didn’t. Aaron predicted that male anoles with larger than average dewlap size would be less likely to survive due to an increased risk of predation. He also predicted that dewlap size would not influence female survival.

Featured scientists: Aaron Reedy and Robert Cox from the University of Virginia. Co-written by undergraduate researcher Cara Giordano.

Flesch–Kincaid Reading Grade Level = 10.3

Additional teacher resource related to this Data Nugget:

For additional images of Robert and Aaron’s research with anoles in Florida, we have created PowerPoint slides that can be shown in class.
Aaron conducted this research as a graduate student in Robert Cox’s lab. To learn more about anole research, visit the lab’s website. To learn more about Aaron, visit his website.
To engage students before the Data Nugget and introduce them to brown anoles, check out this video that shows how brown anoles use dewlap signaling to attract mates and send rival males signals during confrontations:

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11.2.17

When whale I sea you again?

Image of a humpback whale tail from the Palmer Station LTER. Photo credit Beth Simmons.

The activities are as follows:

People have hunted whales for over 5,000 years for their meat, oil, and blubber. In the 19^th and 20^th centuries, pressures on whales got even more intense as technology improved and the demand for whale products increased. This commercial whaling used to be very common in several countries, including the United States. Humpback whales were easy to hunt because they swim slowly, spend time in bays near the shore, and float when killed. Before commercial whaling, humpback whales were one of the most visible animals in the ocean, but by the end of the 20^th century whaling had killed more than 200,000 individuals.

Today, as populations are struggling to recover from whaling, humpback whales are faced with additional challenges due to climate change. Their main food source is krill, which are small crustaceans that live under sea ice. As sea ice disappears, the number of krill is getting lower and lower. Humpback whale population recovery may be limited because their main food source is threatened by ongoing ocean warming.

One geographic area that was over-exploited during times of high whaling was the South Shetland Islands along the Western Antarctic Peninsula (WAP). The WAP is in the southern hemisphere in Antarctica. Humpback whales migrate every year from the equator towards the south pole. In summer they travel 25,000 km (16,000 miles) south to WAP’s nutrient-rich polar waters to feed, before traveling back to the equator in the winter to breed or give birth. Today the WAP is experiencing one of the fastest rates of regional climate change with an increase in average temperatures of 6^° C (10.8^° F) since 1950. Loss of sea ice has been documented in recent years, along with reduced numbers of krill along the WAP.

Logan is a scientist who is studying how humpback whales are recovering after commercial whaling. Logan’s work helps keep track of the number of whales that visit the WAP in the summer. He also determines the sex ratio, or ratio of males to females, which is important for reproduction. The more females in a population compared to males, the greater the potential for having more baby whales born into the next generation. Logan predicts there may be a general trend of more females than males along the WAP as the season progresses from summer to fall. Logan thinks that female humpback whales stay longer in the WAP because they need to feed more than males in order to have extra nutrients and energy before they birth their babies later in the year. This extra energy will be needed for their milk supply to feed their babies.

The Palmer LTER station when Logan and others scientists live while they conduct research on whales.

Humpback whales only surface for air for a short period of time, making it difficult to determine their sex. In order to identify surfacing whales as female or male, scientists need to collect a biopsy, or a sample of living tissue, in order to examine the whale’s DNA. Logan worked with a team of scientists at Oregon State University and Duke University to engineer a modified crossbow that could be used to collect samples. Logan uses this crossbow to collect a biopsy sample each time they spot a whale. To collect a sample, Logan aims the crossbow at the whale’s back, taking care to avoid the dorsal fin, head, and fluke (tail). He mounts each arrow with a 40mm surgical stainless steel tip and a flotation device so the samples will bounce off the whale and float for collection. The samples are then frozen so they can be stored and brought back to the lab for analysis. Logan also takes pictures of each whale’s fluke because each has a pattern unique to that individual, just like the human fingerprint. Additionally, at the time of biopsy, Logan records the pod size (number of whales in the area) and GPS location.

Logan’s data are added to the long-term datasets collected at the WAP. To address his question he used data from 2010-2016 along the WAP and other feeding grounds. Logan’s data ranges from January to April because those are the months he is able to spend at the research station in the WAP before it gets too cold. Logan has added to the scientific knowledge we have about whales by building off of and using data collected by other scientists.

Featured scientist: Logan J. Pallin from Oregon State University. Written by: Alexis Custer

Flesch–Kincaid Reading Grade Level = 10.7

Additional teacher resources related to this Data Nugget:

To see more images of humpback whales, and the Palmer Research Station in the WAP where Logan works, check out this PowerPoint. This can be shared with students in class after they read the Research Background and before they move on to the data.
More data from this region can be found on the DataZoo, Palmer LTER’s online data portal. To access data on this portal, follow instructions found on this “cheat sheet”. For files that have been compiled for educators, check out this Google Drive folder.
For his research, Logan has traveled to United States Antarctic Programs’ Palmer Research Station on the WAP during the austral summer and fall and will be departing again for the WAP in January 2018. He is part of a team of scientists interested in Palmer Long Term Ecological Research, which is funded through the National Science Foundation, documenting changes on in the Antarctic ecosystem.
For more information on whale research at Palmer Station LTER and the WAP, check out this website.
For additional classroom activities dealing with Palmer Station LTER data, check out this website.
The International Whaling Commission (IWC) was created in
1946 in Washington D.C. in hopes to provide conservation to whale stocks around the world. In 1982, the IWC placed a moratorium on commercial whaling. Fore more information on the IWC and humpback whales, check out their website.

About Logan: Logan is interested in determining how humpback whales are recovering after commercial whaling. Logan first got interested in working with marine mammals when he was an undergraduate student at Duke University and had the opportunity to work as a field technician on a project with some scientists at Duke. He quickly realized this was what he wanted to do and that studying humpbac whales was particularly interesting as they appear to have all rebounded quite heavily in the Southern Hemisphere. Assessing why this recovery was happening so fast and why now, was something Logan really wanted to look at. After graduating from college, he continued to work with marine mammologists as a graduate student to receive his Masters in Science from Oregon State University. In the fall of 2017, he started his work on a PhD from University of California, Santa Cruz continuing asking questions and learning more about whales around Antarctica.
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6.27.17

City parks: wildlife islands in a sea of cement

Image of a red fox caught on one of the wildlife cameras.

The activities are as follows:

For most of our existence, humans have lived in rural, natural places. However, more and more people continue to move into cities and urban areas. The year 2008 marked the first time ever in human history that the majority of people on the planet lived in cities. The movement of humans from rural areas to cities has two important effects. First, the demand that people place on the environment is becoming very intense in certain spots. Second, for many people, the city is becoming the main place where they experience nature and interact with wildlife on a regular basis.

Remington and Grant are city-dwellers and have been their entire lives. Remington grew up in Tulsa, Oklahoma and Grant is from Cleveland, Ohio. In Tulsa, Remington fell in love with nature while running on the trails of city parks during cross country and track practices. Grant developed a love for nature while fishing and hiking in the Cleveland Metroparks in Ohio. These experiences led them to study wildlife found in urban environments because they believe that cities can be places where both humans and wildlife thrive. However, to make this belief a reality, scientists must understand how wildlife are using habitats within a city. This knowledge will provide land managers the information they need to create park systems that support all types of species. However, almost all research done on wildlife takes place in natural areas, like national parks, so there is currently very little known about wildlife habits in urban areas. To address this gap in knowledge, Remington, Grant, and their colleagues conduct ecological research on the urban wildlife populations in the Cleveland Metroparks.

Remington prepares to attach the camera to a buckeye tree. He secures them with a heavy-duty lock to keep the cameras safe from theft by people using the parks.

The Cleveland Metroparks are a collection of wooded areas that range in size, usage, and maintenance. Some are highly used small parks with mowed grass, while others are large, rural parks with thousands of acres of forest and miles of winding trails. As they began studying the Metroparks, they noticed the parks were like little “islands” of wildlife habitat within a large “sea” of buildings, pavement, houses and people. This reminded Remington and Grant of a fundamental theory in ecology: the theory of island biogeography. This theory has two components: size and isolation of islands. The first predicts that larger islands will have higher biodiversity because there are more resources and space to support more wildlife than smaller areas. The second is that islands farther away from the mainland will have lower biodiversity because more isolated islands are harder for wildlife to reach. Remington and Grant wondered if they could address this first component in the wide variety of areas that are part of the Cleveland Metroparks. If the theory holds for the Metroparks, it could help them to figure out where most species live in the park system and help managers better maximize biodiversity. It would also provide an important link between ecological research conducted in natural areas and urban ecology.

To evaluate whether the theory of island biogeography holds true in urban areas, Remington and Grant set up 104 wildlife cameras throughout the parks. These cameras photograph animals when triggered by motion. They used these photographs to identify the locations of wildlife in the parks and to get a count of how many individuals there are, known as their abundance. With these data, they tested whether the size of the park would influence biodiversity as predicted by the theory of island biogeography.

One challenge with measuring “biodiversity” is that it means different things to different people. Remington and Grant looked at two common measurements of biodiversity. First, species richness, which is the number of different species observed in each park. Second, they calculated the Shannon Wiener Index of biodiversity for each park. This index incorporates both species richness and species evenness. Species evenness tells us whether the abundances of each species are similar, or if one type is most common and the others are rare. Evenness is important because it tells you whether a park has lots of animals from many different species or if most animals are from a single species. If a park has greater evenness of species, the Shannon-Wiener index will be higher.

Featured scientists: Remington Moll and Grant Woodard from Michigan State University

Flesch–Kincaid Reading Grade Level = 11.4

Additional teacher resource related to this Data Nugget:

Remington and Grant have made their data available for use in classrooms. If you would like to have your students work with raw data, it can be used to calculate the Shannon Wiener Index, or explore other aspects of species richness and evenness in the parks. This data is not yet published, so keep in mind this data is intended only for classroom use. Download the Excel file here!
PowerPoint slideshow of images from the wildlife cameras in the Cleveland Metroparks.
Citizen science Zooniverse site where students can view data and identify species from Remington and Grant’s cameras.
For more background on the importance of biodiversity, students can eat this article in The Guardian – What is biodiversity and why does it matter to us?

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About Remington: Remington is a Ph.D. student and NSF Graduate Research Fellow at Michigan State University in Dr. Bob Montgomery’s lab. Prior to Michigan State, Remington received B.S. and M.S. degrees from the University of Missouri, where he worked with Dr. Josh Millspaugh. Following his M.S., he spent time in Amman, Jordan doing work with the Royal Society for the Conservation of Nature and spent three years teaching high school biology, chemistry, and theology at the Beirut Baptist School in Lebanon.

He uses cutting-edge technologies such as GPS collars and camera-traps to study predator-prey interactions between large carnivores and their prey. He is particularly excited about evaluating how ecological theory developed in “natural” areas like national parks applies to urban contexts. Remington grew up in the city and fell in love with nature and ecology in city parks. Although it carries substantial challenges, Remington believes that humans and large predators can peaceably coexist, even in and around cities. It is his goal to use the lessons learned in his research to help make that belief a reality.

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6.26.17

Why are butterfly wings colorful?

The red postman butterfly, Heliconius erato.

The activities are as follows:

Éste Data Nugget también está disponible en Español:

You’ve probably noticed a bright orange butterfly in your garden. It’s hovering over a plant, and then pausing to lay an egg. It’s landing on a flower, and then sipping the tasty syrup. Big wings allow butterflies to fly everywhere with ease. But you may wonder, why are their wings so brightly colored? One reason why butterflies might have brightly colored wings is that these colors warn birds and other predators that they would not make a tasty meal. Another potential reason for butterflies to have bright colors and dramatic patterns is to attract mates. However, there is little research that shows whether color alone or color pattern together deter predators or attract mates.

Susan holding a different species of butterfly in the field.

The red postman butterfly lives in rainforests in Mexico, Central America, and South America. The color pattern on its wing is usually a mix of red, yellow, and black. These patterns vary a lot depending on their location; for instance one variant has a red bar on the forewings and a yellow bar on its hind wings while another variant has red rays on the hindwings and a yellow bar on the forewings. Scientists Susan, Adriana, and Robert have been studying this species for many years. While hiking in the rainforest, they noticed that not all butterfly species are brightly colored. They started to wonder why the red postman butterfly has bright colors, but other species do not. They thought maybe the red and yellow colors and patterns signaled toxicity to predators, like birds; or these wing features may be used to help find and attract mates. Susan, Adriana and Robert predicted that brightly colored butterflies would be avoided by birds and approached more often by other butterflies of the same species. They also predicted that the local color pattern would get the strongest response from predators and mates, because it would be most recognized in that area.

To test their ideas, the team of butterfly scientists created three kinds of artificial red postman butterfly models using paper and a printer. Each model had a plastic body and paper wings. Model A had the same pattern as the local butterflies at the study site in the La Selva Tropical Biological Station in Sarapiquí, Costa Rica, with brightly colored red and yellow wings. Model B also had the same pattern as the local butterflies, but only had black and white tones. Model C had a different pattern than the locals with bright red and yellow colors.

One of the 400 black and white models in the rainforest during the experiment.

To test for differences in predation attempts based on wing color and patterns, they placed 4 of each model at 100 different sites in the rainforest. This made a total of 1,200 model butterflies with 400 of each type! Models were placed far enough apart that they were not within human visible range from one another (on average separated by 5-10 m), and were positioned approximately 1.5 m above the ground, which is consistent with natural roosting heights. The models were left out in the forest for a total of 96 hours. Each day they were inspected and counted for bird beak marks on their wings and plastic bodies. Only new marks were scored each day, so attacks on individual models were only counted once. To test whether red postman butterflies were more attracted to bright colors, or the local wing pattern, Susan and her student field assistants also caught 51 wild red postman butterflies from the rainforest and brought them to a greenhouse. They then presented the live butterflies with the three models and counted how many times they approached each model type.

Featured scientists: Susan Finkbeiner, Adriana Briscoe, and Robert Reed from University of California, Irvine

Flesch–Kincaid Reading Grade Level = 9.9

Watch two videos of experimental trials from the greenhouse experiment:

The first shows a male butterfly approaching a butterfly paper model with color. The second shows a butterfly as it chooses between a butterfly paper model that is black-and-white and one that has color.

Video Trial 1

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Video Trial 2

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There are two publications related to this Data Nugget:

Finkbeiner SD, Briscoe AD, Reed RD. 2014. Warning signals are seductive: Relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies. Evolution, 68:3410-20. DOI: 10.1111/evo.12524
Finkbeiner SD, Fishman DA, Osorio D, Briscoe AD. 2017. Ultraviolet and yellow reflectance but not fluorescence is important for visual discrimination of conspecifics by Heliconius erato. Journal of Experimental Biology 220: 1267-1276, doi: 10.1242/jeb.153593

You can follow all three scientists on Twitter where they tweet about the latest scientific discoveries involving butterflies, animals, vision and behavior! Adriana @AdrianaBriscoe, Susan @Fink_about_it, and Robert @FascinatingPupa.

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6.9.17

To bee or not to bee aggressive

A honey bee (Apis mellifera) collecting nectar to bring back to the hive. Photo by Andreas Trepte.

The activities are as follows:

Honey bees are highly social creatures that live in large colonies of about 40,000 individuals and one queen. Every member of the hive works together to benefit the colony. Some of the tasks adult bees perform include making honey, nursing young, foraging for food, building honey comb structures, and defending the colony.

From spring through fall, the main task is turning nectar from plants to honey. The honey is stored and eaten over the winter, so it is vital for the colony’s survival. Because honey is an energy-rich food source, hives are targets for break-ins from animals, like bears, skunks, and humans that want to steal the honey. Bees even have to fight off bees from other colonies that try to steal honey. Research shows that colonies adjust their defenses to match threats found in their environment. Hives in high risk areas respond by becoming more aggressive, and hives that do not face a lot of threats are able to lower their aggression. This flexibility makes sure they do not waste energy on unnecessary behaviors.

Clare is a scientist studying the behavior of social animals. There is an interesting pattern seen in other social animals, including humans, that Clare wanted to test in honey bees. In these species, the social environment experienced when an individual is young can have lasting effects on their behavior later in life. This may be because this is the time that the brain is developing. She thought this would likely be the case with honey bees for two reasons. First, bees can use social information to help coordinate group defense. Second, young bees rely completely on adult bees to bring them food and incubate them, so there are a lot of social interactions when they are young. After reading the literature and speaking with other honey bee experts, Clare found out that no one had ever tested this before!

Honey bee larva (top) and an emerging adult (bottom).

Clare chose to look at aggression level as a behavioral trait of individual bees within a colony. She predicted that young honey bees raised in an aggressive colony would be more aggressive as adults, compared to honey bees raised in a less aggressive colony. To test her predictions, Clare used 500 honey bee eggs from 18 different queens. To get these 500 eggs she collected three times in the summer, for two years. Each time she collected, she went to two different locations. Collecting from so many different queens helped Clare make sure her study included eggs with a large genetic diversity.

To test her questions, she used these eggs to set up an experiment. Eggs from each of the 18 queens were split into two groups. Each group was put into one of two types of foster colonies – high aggression and low aggression. Clare determined whether each foster colony was considered high or low aggression using a test. Because half of each queen’s eggs went into a low aggression foster colony, and the other half in a high aggression foster colony, this represents the experimental treatment.

Clare left the foster colonies alone and waited for the bees to develop in the hives. Eggs hatch and turn into larvae. These larvae mature into pupae and then into adults. Just before the young bees emerged from their pupal stage to adulthood, Clare removed them from the foster colonies and brought them into the lab. This way the bees would spend their whole adult life in the lab together, sharing a common environment.

After a week in the lab, Clare tested the aggressiveness of each individual bee. Her test measured aggressive behaviors used by a bee to defend against a rival bee from another colony. Clare observed and counted a range of behaviors including attempts to sting the rival and bites to the rival’s wings and legs. She used these values to calculate an offspring aggression score for each bee.

To select high and low aggression foster colonies to be used in her experiment, Clare first had to identify which colonies were aggressive and which were not. To do this, she put a small amount of a chemical that makes bees aggressive on a piece of paper at the front of the colony entrance. The top two photos show two colony entrances before the chemical. The bottom two photos show the same two colonies 60 seconds after the chemical. The more bees that come out, the more aggressive the colony. You can see from these images that the colony on the right is much more aggressive than the colony on the left. Clare counted the number of bees and used this value to calculate the colony’s aggression score.

Featured scientist: Clare C. Rittschof from the University of Kentucky

Flesch–Kincaid Reading Grade Level = 9.2

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5.5.17

Deadly windows

A white-throated sparrow caught during the experiment. You can see the band on it’s leg, used to make sure they did not record the same bird more than once.

The activities are as follows:

Glass makes for a great windowpane because you can see right through it. However, the fact that windows are see-through makes them very dangerous for birds. Have you ever accidentally run into a glass door or been confused by a tall mirror in a restaurant? Just like people, birds can mistake a see-through window or a mirrored pane for an opening to fly through or a place to get food and will accidentally fly into them. These window collisions can hurt the bird or even kill it. Window collisions kill nearly one billion birds every year!

Urban areas, with a lot of houses and stores, have a lot of windows. Resident birds that live in the area may get to know these buildings well and may learn to avoid the windows. However, not all the birds in an area live there year-round. There are also migrant birds that fly through urban areas during their seasonal migrations. In the fall, for example, migrant birds use gardens and parks in urban areas to rest along their journeys to their winter southern homes. During the fall migration, people have noticed that it seems like more birds fly into windows. This may be because migrant birds, especially the ones born that summer, are not familiar with the local buildings. While looking for food and places to sleep, migrant birds might have more trouble identifying windows and fly into them more often. However, it could also be that there are simply more window collisions in the fall because there are more birds in the area when migrant and resident birds co-occur in urban areas.

Researchers identify the species of each bird caught in one of the nets used in the study. They then place a metal bracelet on one leg so they will know if they catch the same bird again.

Natasha was visiting a friend who worked at a zoo when he told her about a problem they were having. For a few weeks in the fall, they would find dead birds under the windows, more than they would during the rest of the year. He wanted to figure out a way to prevent birds from hitting the exhibit windows. Natasha became interested in learning whether migrant birds were more likely to fly into windows than resident birds or if the number of window collisions only increase in the fall because there are a lot of birds around. To do this she would have to count the total number of birds in the area and also the total number of birds that were killed in window collisions, as well as identify the types of birds. To count the total number of birds in the area, Natasha hung nets that were about the same height as windows. When the birds got caught in the nets, Natasha could count and identify them. These data could then be used to calculate the proportion of migrants and residents flying at window-height. She put 10 nets up once a week for four hours, over the course of three months, and checked them every 15 minutes for any birds that got caught.

Researcher identifying a yellow-rumped warbler, one of the birds captured in the net as part of the study.

Then, she also checked under the windows in the same area to see what birds were killed from window collisions. She checked the windows every morning and evening for the three months of the study. Different species of birds are migratory or resident in the area where Natasha did her study. Each bird caught in nets was examined to identify its to species using its feathers, which would tell her whether the bird was a migrant or a resident. The same was done for birds found dead below windows.

If window collisions are really more dangerous for migrants, she predicted that a higher proportion of migrants would fly into windows than were caught in the nets. But, if window collisions were in the same proportion as the birds caught in the nets, she would have evidence that windows were just as dangerous for resident birds as for migrants.

Featured scientist: Natasha Hagemeyer from Old Dominion University

Flesch–Kincaid Reading Grade Level = 8.7

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below:

Sabo, A.M., Hagemeyer, N.D.G., Lahey, A.S., and E.L. Walters. 2016. Local avian density influences risk of mortality from window strikes. PeerJ 4:e2170; DOI 10.7717/peerj.2170.

To engage students with the lesson before they begin, or after the lesson to help them develop their own independent questions for the system, you can share the following videos:

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5.1.17

Marsh makeover

A saltmarsh near Boston, MA being restored after it was degraded by human activity.

The activities are as follows:

Salt marshes are diverse and productive ecosystems, and are found where the land meets the sea. They contain very unique plant species that are able to tolerate flooding during high tide and greater salt levels found in seawater. Healthy salt marshes are filled with many species of native grasses. These grasses provide food and nesting grounds for lots of important animals. They also help remove pollution from the land before it reaches the sea. The grass roots protect the shoreline from erosion during powerful storms. Sadly today, humans have disturbed most of the salt marshes around the world. As salt marshes are disturbed, native plant biodiversity, and the services that marshes provide to us, are lost.

A very important role of salt marshes is that they are able to store carbon, and the amount they store is called their carbon storage capacity. Carbon is stored in marshes in the form of both dead and living plant tissue, called biomass. Marsh grasses photosynthesize, taking carbon dioxide out of the atmosphere and storing it in plant biomass. This biomass then falls into the mud and the carbon is stored there for a very long time. Salt marshes have waterlogged muddy soils that are low in oxygen. Because of the lack of oxygen, decomposition of dead plant tissue is much slower than it is in land habitats where oxygen is plentiful. All of this stored carbon can help lower the levels of carbon dioxide in our atmosphere. This means that healthy and diverse salt marshes are very important to help fight climate change.

However, as humans change the health of salt marshes, we may also change the amount of carbon being stored. As humans disturb marshes, they may lower the biodiversity and fewer plant species can grow in the area. The less plant species growing in the marsh, the less biomass there will be. Without biomass falling into the mud and getting trapped where there is little oxygen, the carbon storage capacity of disturbed marshes may go down.

Jennifer, working alongside students, to collect biomass data for a restored saltmarsh.

It is because of the important role that marshes play in climate change that Jennifer, and her students, spend a lot of time getting muddy in saltmarshes. Jennifer wants to know more about the carbon storage capacity of healthy marshes, and also those that have been disturbed by human activity. She also wants to know whether it is possible to restore degraded salt marshes to help improve their carbon storage capacity. Much of her work focuses on comparing how degraded and newly restored marshes to healthy marshes. By looking at the differences and similarities, she can document the ways that restoration can help increase carbon storage. Since Jennifer and her students work in urban areas with a lot of development along the coast, there are lots of degraded marshes that can be restored. If she can show how important restoring marshes is for increasing plant diversity and helping to combat climate change, then hopefully people in the area will spend more money and effort on marsh restoration.

Jennifer predicted that: 1) healthy marshes will have a higher diversity of native vegetation and greater biomass than degraded salt marshes, 2) restored marshes will have a lower or intermediate level of biomass depending on how long it has been since the marsh was restored, and 3) newly restored marshes will have lower biomass, while marshes that were restored further in the past will have higher biomass.

To test her predictions, Jennifer studied two different salt marshes near Boston, Massachusetts, called Oak Island and Neponset. Within each marsh she sampled several sites that had different restoration histories. She also included some degraded sites that had never been restored for a comparison. Jen measured the total number of different plant species and plant biomass at multiple locations across all study sites. These measurements would give Jen an idea of how much carbon was being stored at each of the sites.

Featured scientist: Jennifer Bowen from Northeastern University

Flesch–Kincaid Reading Grade Level = 11.0

12.6.16

Sticky situations: big and small animals with sticky feet

Travis in the lab measuring the stickiness of a gecko’s toe.

The activities are as follows:

Species are able to do so many amazing things, from birds soaring in the air, lizards hanging upside-down from ceilings, and trees growing hundreds of feet tall. The study of biomechanics looks at living things from an engineering point of view to study these amazing abilities and discover why species come in such a huge variety of shapes and sizes. Biomechanics can improve our understanding of how plants and animals have adapted to their environments. We can also take what we learn from biology and apply it to our own inventions in a process called biomimicry. Using this approach, scientists have built robotic jellyfish to survey the oceans, walking robots to help transport goods, and fabrics that repel stains like water rolling off a lotus leaf.

Travis studies biomechanics and is interested in the ability of some species to climb and stick to walls. Sticky, or adhesive, toe pads have evolved in many different kinds of animals, including insects, arachnids, reptiles, amphibians, and mammals. Some animals, like frogs, bats, and bugs use suction cups to hold up their weight. Others, like geckos, beetles, and spiders have toe pads covered in tiny, branched hairs. These hairs actually adhere to the wall! Electrons in the molecules that make up the hairs interact with electrons in the molecules of the surface they’re climbing on, creating a weak and temporary attraction between the hairs and the surface. These weak attractions are called van der Waals forces.

Travis catching lizards in the Dominican Republic.

The heavier the animal, the more adhesion they will need to stick and support their mass. With a larger toe surface area, more hairs can come in contact with the climbing surface, or the bigger the suction cup can be. For tiny species like mites and flies, tiny toes can do the job. Each fly toe only has to be able to support a small amount of weight. But when looking at larger animals like geckos, their increased weight means they need much larger toe pads to support them.

When comparing large and small objects, the mass of large objects grows much faster then their surface area does. As a result, larger species have to support more mass per amount of toe area and likely need to have non-proportionally larger toes than those needed by lighter species. This results in geckos having some crazy looking feet! This relationship between mass and surface area led Travis to hypothesize that larger species have evolved non-proportionally larger toe pads, which would allow them to support their weight and stick to surfaces.

To investigate this idea, Travis looked at the data published in a paper by David Labonte and fellow scientists. In their paper they measured toe pad surface area and mass of individual animals from 17 orders (225 species) including insects, arachnids, reptiles, amphibians, and mammals. From their data, Travis calculated the average toe pad area and mass for each order.

Travis then plotted each order’s mass and toe pad area on logarithmic axes so it is easier to compare very small and very large values. Unlike a standard axis where the amount represented between tick marks is always the same, on logarithmic axes each tick mark increases by 10 times the previous value. For example, if the first tick represents 1.0, the second tick will be 10, and the next 100. As an example, look at the graphs below.

The left plot shows hypothetical gecko species of different sizes, but with proportional toes. Their mass per toe pad area ratio (g/mm²) varies, with larger species having larger g/mm² ratios. In this case, larger species have to support more mass per toe pad area. In the right plot, larger gecko species have disproportionally larger toes. These differences change each species’ mass per toe pad area ratios, so that all species, regardless of their size, have the same mass per toe pad area ratio.

Featured scientists: David Labonte, Christofer J. Clemente, Alex Dittrich, Chi-Yun Kuo, Alfred J. Crosby, Duncan J. Irschick, and Walter Federle. Written by: Travis Hagey

Data Nugget Flesch–Kincaid Reading Grade Level = 10.3

Scaling Up – Math Activity Flesch–Kincaid Reading Grade Level = 9.5

There is a scientific paper associated with the data in this Data Nugget. The data was used with permission from D. Labonte.

Labonte, D., Clemente, C.J., Dittrich, A., Kuo, C.Y., Crosby, A.J., Irschick, D.J. and Federle, W., 2016. Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing. Proceedings of the National Academy of Sciences, p.201519459.

To learn more about Travis and his research on geckos, read this blog post, “An evolving sticky situation” and check out the video below!

Sticky situations video

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For a video and article on using “gecko power” to scale a building, check out this article – Climbing a Glass Building? Try a Gecko’s Sticky Pads

About Travis: Ever since Travis was a kid, he was interested in animals and wanted to be a paleontologist. He even had many dinosaur names memorized to back it up! In college he discovered evolutionary biology, which drove him to apply for graduate school and become a scientist. There, he fell in love with comparative biomechanics, which combines evolutionary biology and mechanical engineering. Today Travis studies geckos and their sticky toes that allow them to scale surfaces like glass windows and tree branches.

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12.2.16

Are you my species?

Michael holding a male darter. The bright color patterns differ for each of the over 200 species. Photo by Tamra Mendelson.

The activities are as follows:

What is a species? The biological species concept says species are groups of organisms that can mate with each other but do not reproduce with members of other similar groups. How then do animals know who to choose as a mate and who is a member of their own species? Communication plays an important role. Animals collect information about each other and the rest of the world using multiple senses, including sight, sound, sonar, and smell. These signals may be used to figure out who would make a good mate and who is a member of the same species.

Michael snorkeling, looking for darters.

Michael is a scientist interested in studying how individuals communicate within and across the boundaries of species. He studies darters, a group of over 200 small fish species that live on the bottom of streams, rivers, and lakes. Michael first chose to study darters because he was fascinated by the bright color patterns the males have on their bellies during the breeding season. Female darters get to select which males to mate with and the males fight with each other for access to the females during the mating season. Species identification is very important during this time. Females want to make sure they choose a member of their own species to mate with. Males want to make sure they only spend energy fighting off males of their own species who are competing for the same females. What information do females and males use to guide their behavior and how do they know which individuals are from their own species?

Across all darter species, there is a huge diversity of color patterns. Because only males are brightly colored and there is such a diversity of colors and patterns, Michael wondered if males use the color patterns to communicate species identity during mating. Some darter species have color patterns that are very similar to those of other darter species. Perhaps, Michael thought, the boundaries of species are not as clear as described by the biological species concept. Some darter species may be able to hybridize, or mate with members of a different species if their color patterns are very close. Thus, before collecting any data, Michael predicted that the more similar the color patterns between two males, the more likely they would be to hybridize and act aggressively towards each other. If this is the case, it would serve as evidence that color pattern may indeed serve as a signal to communicate darter species identity.

Michael (right) in the field, collecting darters. Photo by Tamra Mendelson.

Michael collected eight pairs of darter species (16 species in all) from Alabama, Mississippi, Tennessee, Kentucky, South Carolina, and North Carolina and brought them all back to the lab. In some species pairs the color patterns were very similar, and in some they were very different. For each species pair, he put five males of both species and five females of both species in the same fish tank and observed their behavior for five hours. He did this eight times, once for each species pair (for a total of 1,280 fish!). During the five-hour observation period, he recorded (1) how many times females mated with males of their own species or of a different species and (2) how many times males were aggressive towards males of their own species or of a different species. He used these data to calculate an index of bias for each behavior, to show whether individuals had stronger reactions towards members of their own species.

Featured scientist: Michael Martin from the University of Maryland, Baltimore County

Flesch–Kincaid Reading Grade Level = 10.9

Videos showing darter behavior:

Darter species used in the experiment:

darters

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