New England wildlife and rock walls: how do they share the forest?

Throughout the forests of New England, rock walls are commonly found (broken down as they may be) as remnants of past farm boundaries. Forest flora and fauna soon recolonised the fields after many of the farms were abandoned for alternate land in the western United States. Today, this occurrence can be witnessed in University of Rhode Island’s very own backyard: North Woods. We worked with Dr. Brian Gerber and his graduate students Juliana Masseloux and Erin Wampole to develop an independent research project to characterize the wildlife in the area and to understand how they are using the remnant rock walls scattered in the forest.

We explored the following questions: what mammals are in North Woods despite its proximity to a potentially disturbing campus and are/how are these mammals using the rock walls that may fragment their habitat?

White tailed deer crossing through a gap in a remnant rock wall, North Woods, Kingston, RI

White tailed deer crossing through a gap in a remnant rock wall, North Woods, Kingston, RI

A map of North Woods (Kingston, RI) showing the camera locations in green icons and the most adjacent remnant rock walls in yellow

A map of North Woods (Kingston, RI) showing the camera locations in green icons and the most adjacent remnant rock walls in yellow

To dive into these questions, we deployed ten trail cameras throughout North Woods that pointed at either 1) a stretch of solid rock wall, or 2) a gap in a rock wall with what appeared to be a game trail running through it. We compared the mammal species seen on the cameras to determine which animals preferentially used solid parts of the rock walls or gaps in the walls. The cameras recorded still photos at the sites for about 4 weeks. We checked each camera weekly and tagged pictures with information such as species, group size, whether the pictures were of a stretch of a solid rock wall or a trail through a rock wall, etc. Rather than using the number of individuals in our analysis, we analyzed the number of groups. This means that if there were four deer in one picture, we counted that as one group.

 

Our pictures revealed what we had initially hypothesized: more animals were using gaps in the walls to travel through rather than using the solid walls to travel on top of or over.

These animals may be too heavy to travel on top of the wall, or perhaps it takes too much energy to do so.

The mammals that tended to travel on the top of rock walls were more agile. This method of transportation could be used because there is less resistance traveling on top of the wall than on the forest floor.

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URI student

admires the wall

Despite the study area’s proximity to the URI campus, many typical New England forest species were detected:

The number of times a group of animals was detected at our camera sites either placed at a gap in the wall (Trail, orange bars) or at a solid stretch of the wall (W, blue bars). The number of groups of animals was analyzed, not the number of individuals. This most likely led to some underestimates of the animals often found in groups of multiple individuals such as deer. The majority of animals recorded at gaps in the walls were passing through the gaps while the majority of animals captured at continuous rock walls were traveling on top of the walls. However, some individuals at both site types used the forest surrounding the rock wall for activities such as foraging or locomotion.

The number of times a group of animals was detected at our camera sites either placed at a gap in the wall (Trail, orange bars) or at a solid stretch of the wall (W, blue bars). The number of groups of animals was analyzed, not the number of individuals. This most likely led to some underestimates of the animals often found in groups of multiple individuals such as deer. The majority of animals recorded at gaps in the walls were passing through the gaps while the majority of animals captured at continuous rock walls were traveling on top of the walls. However, some individuals at both site types used the forest surrounding the rock wall for activities such as foraging or locomotion.

Future projects: We may use the group size instead of number of groups to more accurately estimate species abundance. Another aspect we would like to investigate during our next study period is how species are using each wall. Are they using it as a funnel, because the walls are too large to get around otherwise? Or are predators using them to hunt, and prey using them as hiding spots? The answers to these questions could give more insight into wildlife management. If the walls are prohibiting wildlife from moving around, or disrupting the food web at all, we should consider the possibility of their removal.

Jessica Burr  is an undergraduate student interning in  Dr. Brian Gerber’s lab  studying Wildlife and Conservation Biology at the University of Rhode Island.

Jessica Burr is an undergraduate student interning in Dr. Brian Gerber’s lab studying Wildlife and Conservation Biology at the University of Rhode Island.

Ruby Nguyen  is an undergraduate student interning in  Dr. Brian Gerber’s lab  at the University of Rhode Island double majoring in Biology and Wildlife Conservation Biology.

Ruby Nguyen is an undergraduate student interning in Dr. Brian Gerber’s lab at the University of Rhode Island double majoring in Biology and Wildlife Conservation Biology.

 
Erin Wampole  was Jessica and Ruby’s co-mentor for the North Woods camera trapping project. She is a Master’s student researching carnivore biology and applied ecology in  Dr. Brian Gerber’s lab .

Erin Wampole was Jessica and Ruby’s co-mentor for the North Woods camera trapping project. She is a Master’s student researching carnivore biology and applied ecology in Dr. Brian Gerber’s lab.

Juliana Masseloux  was Jessica and Ruby’s co-mentor for the North Woods camera trapping project. She is a Master’s student researching conservation in human-wildlife conflicted areas in  Dr. Brian Gerber’s lab .

Juliana Masseloux was Jessica and Ruby’s co-mentor for the North Woods camera trapping project. She is a Master’s student researching conservation in human-wildlife conflicted areas in Dr. Brian Gerber’s lab.

 

Robots reveal: commonly used pesticides harm bee behavior and metabolism

Scientists, automated robots, and mini-backpacks equipped with tiny QR codes team up to finally understand how pesticides harm the lives of bees. Read the full scientific article here and check out the lead author’s, James Crall’s, website for details and more awesome video.

Crall JD, Switzer CM, Oppenheimer RL, Ford Versypt A, Dey B, Brown B, Eyster M, Guérin C, Pierce NE, Combes SA, de Bivort BL (2018).  Neonicotinoid exposure disrupts bumblebee nest behavior, social networks, and thermoregulationScience 362, 683–686. PDF

Photo by James Crawl: Bumblebee  (Bombus impatiens)  wearing a simplified QR code for individual recognition and tracking

Photo by James Crawl: Bumblebee (Bombus impatiens) wearing a simplified QR code for individual recognition and tracking

 

Neonicotinoid pesticides are widely used to protect our crops from insect pests, but neonicotinoids don’t discriminate, as they also target beneficial insects like pollinating bees. This class of pesticides disrupts an animal’s nervous system affecting their behaviors and physiology.

USDA estimated annual imidacloprid use in the US for 2016.

USDA estimated annual imidacloprid use in the US for 2016.

 

The neonicotinoid imidacloprid is applied to an estimated 1 million pounds of vegetables, fruit, and soy annually in the US, and the pesticide can remain in plant tissue for up to 230 days after application.

USDA estimated annual imidacloprid use by crop in the US, 2016. Celebrate in that the total estimated annual imidacloprid use has decreased by 1 million pounds of food in recent years.

USDA estimated annual imidacloprid use by crop in the US, 2016. Celebrate in that the total estimated annual imidacloprid use has decreased by 1 million pounds of food in recent years.

Harvard scientists developed an automated robot to continuously track the behavior of bees to characterize the negative effects of eating ecologically relevant levels of imidacloprid (levels of imidacloprid that they would encounter in the wild).

Specifically, researchers determined that consuming this pesticide harmed bee behavior and the colony’s ability to regulate their nest temperature. Tracking data gathered by the robot revealed that eating imidacloprid impaired normal bee behavior after both a single exposure and repeated exposure to the pesticide.

Example using the BEEtag software (https://github.com/jamescrall/BEEtag) to track individual bumblebees 24 hours after consuming 0.1 ng (blue) or 1.0 ng (red) of imidacloprid, or a control sucrose solution (green).

Bees that consumed daily doses of imidacloprid and bees that ate one single dose of imidacloprid both decreased the amount of time they spent active, the time they spent nursing, and the proportion of time they interacted with other bees compared to bees eating normal nectar. Bees eating imidacloprid also spend more time on the outside of the colony away from the food storage hub and nursery.

Crall et al. 2018, Figure 1 D-G. Colony mean percentage of time active over 7 consecutive days (with time indicating hours after exposure) during the daily imidacloprid exposure experiment . Filled circles represent mean activity levels for a single colony (averaged across all individual workers) for a single 5-min trial, and solid lines show mean values for treatment groups (control colonies, n = 9, in green; imidacloprid-exposed colonies, n = 9, in red). Gray blocks and Sun/Moon symbols show the 14:10 hour L:D cycle in the tracking arena. (E) Percentage of time engaged in nursing. (F) Mean distance to the nest center and (G) social network density [proportion of possible pairwise interactions between workers that actually occur, during a single 5-min trial

Crall et al. 2018, Figure 1 D-G. Colony mean percentage of time active over 7 consecutive days (with time indicating hours after exposure) during the daily imidacloprid exposure experiment . Filled circles represent mean activity levels for a single colony (averaged across all individual workers) for a single 5-min trial, and solid lines show mean values for treatment groups (control colonies, n = 9, in green; imidacloprid-exposed colonies, n = 9, in red). Gray blocks and Sun/Moon symbols show the 14:10 hour L:D cycle in the tracking arena. (E) Percentage of time engaged in nursing. (F) Mean distance to the nest center and (G) social network density [proportion of possible pairwise interactions between workers that actually occur, during a single 5-min trial

An experiment set in the field with natural conditions revealed that bee physiology is also harmed by short term pesticide consumption. Bee colonies weren’t able to regulate their nest’s temperature after 1-2 hours of intermittent feeding on nectar containing imidacloprid. Whereas, colonies feeding on normal nectar maintained nest temperatures above outdoor temperatures.

Crall et al. 2018, Figure 3 C. Brood versus outdoor temperatures for control, normal nectar fed colonies (C, green) and treated, imidacloprid fed (IM, red). Transparent markers show individual measurements across all colonies, and solid lines show LOESS-smoothed trends by treatment.

Crall et al. 2018, Figure 3 C. Brood versus outdoor temperatures for control, normal nectar fed colonies (C, green) and treated, imidacloprid fed (IM, red). Transparent markers show individual measurements across all colonies, and solid lines show LOESS-smoothed trends by treatment.

These elegant series of experiments present new automated technology that enables scientists to answer detailed questions about context specific insect behavior, movement, and social dynamics. The future possibilities are endless: How will bees respond to other pesticides, contaminates, or disease? How do these challenges affect other insect species? How do different insect species socially interact?

But also as a take-home message: don’t use or support neonicotinoid pesticides.
EPA’s action to protect pollinators & ways you can help

Erik Stokstad AAS Science provides an overview of the study, https://www.sciencemag.org/news/2018/11/new-tracking-system-could-show-last-how-pesticides-are-harming-bee-colonies

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About the author:
Kristen J. DeMoranville @Kris10DeMo is a Ph.D. student researching the effects of diet and long-distance flight on a migratory songbird in Scott McWilliams lab at the University of Rhode Island

Source: https://docs.wixstatic.com/ugd/f7293c_5c22905f830440dc8f24131ae5661c0b.pdf

Clay Graham: avian ecologist

Interview conducted by Erin Harrington, science communicator and bird ecologist

I recently interviewed Clay Graham, a Master’s student in the Biological and Environmental Sciences program at URI. He is part of a collaborative research project between URI and RI Department of Environmental Management that has been going on for about a decade now. Researchers are trying to learn all they can about a weird shorebird found in the forest called the American Woodcock. This bird uses young forest habitats for feeding, courting, and rearing its young. In the past, researchers have been studying woodcock movement during mating season, woodcock habitat use, and how those both connect when it comes to forest management. But, Clay’s research will be going a step further – he’ll be studying woodcock movement not only during breeding season, but also during migration. In Clay’s own words:

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“I study what habitats and resources Rhode Island American Woodcock use over the course of a year, how habitat and resource use change for woodcock in different landscapes, and what characterizes Rhode Island woodcock migratory behavior by using radio transmitters and GPS tags.”

-Clay Graham

Photo credit Steve Brenner

 Here is what I asked Clay about his research…

 How and when did you first become interested in birds?
One of my classmates in second grade gave a presentation on penguins, and despite including a range map, I looked for them in my backyard. While searching my backyard I noticed a Red-tailed Hawk in the oak tree behind my house and asked my mom for help in identifying the bird. This was my spark bird! After this, I spent a lot of time as a kid in my backyard and the Cuyahoga Valley National Park identifying trees, wildflowers, and wildlife and loved flipping through my Sibley guide my parents bought me, wondering how many of the species of birds might have passed through my backyard at one point in time. I may or may not have began conversations with friends growing up with, “so, have you seen any wildlife lately”?

American Woodcock wearing a VHF radio transmitter blending in with the forest floor.  Photo credit Josh Cummings

American Woodcock wearing a VHF radio transmitter blending in with the forest floor. Photo credit Josh Cummings

I also loved the hidden knowledge that CVNP [Cuyahoga Valley National Park] rangers, Ted Williams seasonal natural history column in Audubon magazine, and local naturalists had about natural history. They seemingly knew about all these incredible processes and local species distributions, and really knew the story and dynamics of a landscape. I still feel this as a 29 year old Master’s student working with the American Woodcock, a species which is incredibly easy to mistake as being part of the forest floor, and is often overlooked except for those who are familiar with their natural history. 

 When and why did you first become interested in woodcock, and this study specifically?
One of the first woodcock I saw as a kid was a bird migrating between buildings in lower Manhattan on a family trip in eighth grade; a highly unpredictable landscape for any bird to navigate.

For many shorebirds, including woodcock, I’ve always been interested in how shorebirds find suitable stopover habitat, what decisions they make during migration, and how they handle the unpredictable nature of finding suitable stopover.

Although woodcock have been mostly studied from a perspective around habitat selection, woodcock are a really interesting system to study migration especially as there are populations which are migratory, non-migratory, short and long distance migrants, counter to most birds they have a prolonged spring migration in comparison to a rather quick fall migration.

They also are really unique in that they have assumed a migratory behavior by tracking the invasion of non-native earthworms after the glacial retreat extirpated native earthworms from the north, which always blows my mind.

 What interesting things have you found out in your research so far?
Preliminarily, using data from my first field season, it seems that woodcock can make quick migratory leaps often travelling 400 miles in a night, or using one stopover site before arriving at their wintering grounds, as well as woodcock left Rhode Island anywhere from early November to early December.

In addition, it seems that birds from higher quality habitats tended to migrate earlier than birds from lower quality habitats and are mostly wintering along the coast, anywhere from Connecticut to Alabama.

RI caught American Woodcock (circles) and their movements in during fall migration (November-December 15), informed by GPS transmitters.  Map created by Clay Graham

RI caught American Woodcock (circles) and their movements in during fall migration (November-December 15), informed by GPS transmitters. Map created by Clay Graham

What excites you most about your current research? What excites you most about Woodcock?
I think what’s exciting to me is how many unexplored questions there are for something that is seemingly so well studied, and especially how strange woodcock are as a system. For instance, woodcock are a really interesting system to study breeding behavior as they exhibit reverse sexual dimorphism [females are larger than males], are polygynous [1 male mates with multiple females], and fly to fields to perform aerial courtship displays.

Due to woodcock displaying in the evening (making them difficult to see), little is known about the presence or absence of females at each singing ground, male breeding success depending on site quality, the birds condition and, age and how breeding intensity and behaviors change over the course of the breeding season. This has implications in understanding which males are most or least likely to mate, and how females choose which display site to breed at, and there’s a ton of room to look at ethology in these birds. Or the fact that they are shorebirds that spend most of their time in forests.

I also love how dynamic they are. When tracking them over the summer, it would seem that just when you think a particular woodcock has settled into a location, the bird would move to another habitat within a landscape, especially as the water table drops in summer. It’s also really exciting to be working with novel tracking technology, and to hope that information from my research will be able to contribute to broader scientific discussions and management plans for woodcock.

 Could you describe what a typical day in the field is like?

[In the spring Clay catches individuals for the first time]: Depending on cloud cover and the moonphase, right at about 18-25 minutes after sunset, (or often I used when I can’t see details such as hairs on my outstretched hands or the print on a piece of paper), woodcock start ‘peenting’ and flying to fields to perform their aerial displays. I then usually wait until I see the poles wiggle a little bit, or an absence of displays to check the nets indicating that a bird might be in my mist net.  Sometimes we have to use speakers of ‘peent’ calls to catch woodcock as a last resort, as well.

My summers are spent tracking spring caught birds that had radio-transmitters attached to them, through swamps and thickets and scrubby habitat. This is in an effort to identify their diurnal [daytime] foraging locations, in order to build summer home ranges. Woodcock can be anywhere from deep, deep forest to industrial sites and peoples backyard, and some will periodically change their diurnal habitat. Sometimes you are walking through forest and wading through creeks for an hour to reach a bird, while other times the bird is right beside a road and take about two minutes to find and gather a location: each bird seems to have their own story.

Read more about how the McWilliams’ lab uses radio telemetry here

Gerald H. Krausse

What difficulties did you run across in your research? How did you surmount those challenges to reach your current insights?
Fall this year was pretty challenging in that I wasn’t sure I would be able to recatch woodcock I tracked over the summer in order to replace their radio-transmitters with GPS tags. The first two weeks of September I spent trying to catch a female I tracked over the summer, which loved to roost in log landings that had been clear-cut with intact logs  and briars. I never caught this female as it was in too difficult of an area to catch it, but after moving on to other birds I tracked over the summer, I managed to catch 9/12 birds that had transmitters on them.  

We tried all sorts of deigns and tactics, but what eventually worked best was to capture birds on nights with no ambient light where it was raining, using a speaker to make background noise to cover up my footsteps and to have three people tracking the bird to pinpoint it’s exact location and stop the bird. If conditions were right I would stay out all night to catch several birds, especially as September is the driest month, I had to be efficient with the best conditions for catching.

 What happens next? What still needs to be studied, and where will the research go next?
The hard work is done for this field season, with the Argos satellites doing much of the heavy lifting by downloading and sending information from our GPS tags. Winter will consist of entering data into GIS, and beginning some preliminary analysis of homeranges, and habitat selection. Next field season will be much of the same except I would like try to and catch more birds, as well as create a resource selection function for nocturnal roosts.

Anecdotally, it seems that birds are highly selective with roosting locations, and yet incredibly varied. This fall I encountered birds roosting next to rivers in open grassy floodplains, open fields, under holly bushes in clear cuts, along old abandoned roads in pepperbush thickets and in wetlands that were no longer inundated with water. We need to have a better understanding of roost site selection, as the lack of open fields and disturbed locations for roosting and breeding is one of the main reasons woodcock have been in decline.

Why is your research pertinent beyond informing us about the habitat woodcock need?
Woodcock have been found to be representative species of early successional [young forest] habitat, a critical and declining habitat throughout New England. As forests mature and humans limit their disturbance in New England, no longer clear cutting forests to maintain agriculture, the habitat and species associated with early successional habitat have similarly declined. Conservation of woodcock by proxy also conserves declining species like Wood Turtles, New England Cottontail, and many migratory species of birds which use early successional habitat  for both nesting, and providing food for nestlings, as well as adds diversity to a largely monotonous landscape.  

Is there anything else you would like to say? Are there any questions you would have liked to answer that I didn't ask you?
As part of a multi-state collaboration, URI has been working with the Eastern Woodcock Migratory Research Project, to understand eastern woodcock migratory movements.

 

Clay Graham is a master’s student studying the annual cycle movements of Rhode Island breeding American Woodcock, and how body condition affects fall migratory movements in  Scott McWilliams lab  at the University of Rhode Island  Photo credit Patrick Woodward

Clay Graham is a master’s student studying the annual cycle movements of Rhode Island breeding American Woodcock, and how body condition affects fall migratory movements in Scott McWilliams lab at the University of Rhode Island Photo credit Patrick Woodward

Interview conducted by Erin Harrington, a Ph.D. student studying science communication and avian ecology in the  Scott McWilliams lab  at the University of Rhode Island

Interview conducted by Erin Harrington, a Ph.D. student studying science communication and avian ecology in the Scott McWilliams lab at the University of Rhode Island

What can we learn from animal home ranges?

Integral to all of our daily, monthly, and yearly activities is the locations where we perform our tasks, be they recreational, professional, or personal maintenance. We don’t necessarily have to define ourselves based solely on our locations, and even though Dave Matthews would probably disagree, where we are can certainly provide plenty of information about our lives.

Birds are no different. They go to certain locations to sleep. They go to certain locations to eat breakfast. And even though birds don’t have an economy or traditional ‘jobs’, they still have work to do. Thus, if we can figure out where an individual bird is, and better yet, why that individual is there, we can start to piece together the rich tapestry that is the life of a bird. And with more information about where birds go and how they get there, conserving habitat and populations becomes that much easier and more effective.

A Prairie warbler surveys his breeding territory. Pennsylvania, summer.  Photo credit: Steve Brenner

A Prairie warbler surveys his breeding territory. Pennsylvania, summer. Photo credit: Steve Brenner

            First big point to establish: this is all about tracking individuals and then using that spatial information to answer a variety of questions about birds. Tracking animal movements at the population or species level is possible, albeit with slightly different methodological frameworks, but we can save that for another post. There are many ways to track individual birds, and the methodology is usually defined by the questions you want to answer and the technology available. This is quite a robust topic with a deep history, but alas, we must contain the ever-growing urges of scientific curiosity bubbling inside and focus on the overall purpose of tracking individuals. What kind of information can we gain, and what can we say or do with that information?

            Let’s look at one of the basic and fundamental measurements in spatial ecology - an individual’s home range. The simplest definition of a home range is the space where an animal lives. Think of the daily routine example from above. Where we sleep, eat, and work exists within a certain space. Usually this space is contained within a town or city, and within that space would be your house, your office, your favorite places for recreation. Likewise, a bird’s home range is the space that contains the locations where it forages, nests, preens its feather, and sleeps.

            To generate a home range, the first things we need are the locations in space and time of an individual (think GPS points on a map). Next, we need to choose a period of time we are interested in. For migratory birds, this could be a variety of periods throughout the year that each encompass different ecological behaviors and have different implications. For example, the breeding season, roughly May-August for North American birds, would be the time to construct a classic home range that contains a nest location, feeding areas, and locations for protecting young from predators.

Nestling Dark-eyed juncos, hoping their parents picked a safe nest location. Arizona, summer.  Photo credit: Steve Brenner

Nestling Dark-eyed juncos, hoping their parents picked a safe nest location. Arizona, summer. Photo credit: Steve Brenner

To properly construct a home range, we need to make sure we have enough locations that we are gathering (or sampling from) that are representative of the bird over different times of the day and over the entire period of interest. Once we have our representative locations, we can plot them on a map and build the home range. But enough with the words, Steve, give us an example!

I’ve been studying towhees for the past two years in an effort to assess the effectiveness of statewide early successional/young forest management strategies for songbirds. Towhees are perfect representative of young forest or shrubland birds. Think of all the thorny, scrubby, bushy places you avoid on a daily basis…this type of habitat is perfect for towhees, and it’s in short supply in southern New England. Gathering spatial and nesting data on towhees and other shrub birds in Rhode Island will help us understand how (and if) these animals are using state-managed forests.

Male Eastern towhee, looking sharp and ready to provide spatial data with his new transmitter. Rhode Island, summer.  Photo credit: Steve Brenner

Male Eastern towhee, looking sharp and ready to provide spatial data with his new transmitter. Rhode Island, summer. Photo credit: Steve Brenner

Let’s look at the locations of an adult male Eastern towhee between June and August 2016 in Rhode Island. This individual was tracked after he successfully fledged 2 young, and was subsequently caring for his fledglings. Here are some of his GPS locations mapped out.

ptsonetowARC.png

Already this is pretty cool to visualize. Just from seeing his points in context with aerial imagery is neat on its own. Also, the imagery provides a general context for the type of forest towhees are hanging around. But let’s create his home range and see what else we can find out. The simplest way to do this is by a method called ‘Minimum Convex Polygon”, or MCP. Essentially, this entails drawing the smallest box possible around all of our sampled points.

mcp.png

Cool! Already we can look at this map and say some things about this bird’s life. For instance: the size of this polygon is just about 1 hectare, which is roughly the size of a football field. Thus, this particular bird seemed to consistently spend a lot of time within a hectare-sized area while his young slowly grew up over the summer. But this whole straight-lined polygon thing seems a bit…unnatural. What are the odds that this towhee didn’t stray outside the blue lines on the map, or put another way, the likelihood the summer home range of this bird doesn’t include space beyond these lines? Fortunately, scientists have devised other ways to estimate home ranges beyond MCPs. A common method to account for the likelihood of an animal occurring outside this arbitrary polygon is by using kernel density estimation, or KDE. These methods can be a little complex and depend on many factors including sample size (how many points did you gather per bird?), autocorrelation (the influence of one location on the next), and bandwidth estimators (for statistics!).

I know what you’re thinking: we have reached the section of the article filled with multi-syllabic words that sound like math and are intentionally complex, and the only people who understand this are folks that like tofu and listen to jazz. Fear not. The extremely short explanation of KDE is that by using the distances between the sample locations themselves, one can more accurately estimate the probability of space used by an animal, and thus build a better home range. So let’s rebuild this towhee’s home range using KDE.

HRonetowARC.png

            Well isn’t this just a pretty looking bit of spatial data! The size of this polygon is 2.8 hectares, which is much larger than the square box from earlier. But think about why this makes more sense. Giving the layout of this points, the odds that this bird wouldn’t use areas outside the GPS points I sampled it at are slim. These points are daily samples of one point in space - not direct minute-by-minute tracks of the bird, or even it’s path from one point to the next. Thus, this type of home range estimation takes this fact into account and by the magic of statistics you get this purple polygon. With a measurement of home range, we can compare this bird’s movements to other towhees that are raising young, or even to other towhees but during different stages of the life cycle (for example: does the home range size between the post-fledging period and the nesting period? I don’t know, but that’s a great question for future research!)

Think about the habitat/environmental questions we can answer with this home range. What if I wanted to know how much towhees utilized previously managed forest clearcuts? Well, first I can add this GIS layer that outlines areas that were previously managed by the state.

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Sweet! Then I could overlap with the home range, and calculate a quick percentage (~65%). Seems like this critter was happy to use a regenerating clearcut to raise his young, which makes a whole lot of sense. Early successional forests are full of densely packed shrubs and young trees. This provides excellent cover for vulnerable, recently fledged baby birds.

A fledgling towhee, wondering if it's about to be fed or eaten. Rhode Island, summer.  Photo credit: Steve Brenner

A fledgling towhee, wondering if it's about to be fed or eaten. Rhode Island, summer. Photo credit: Steve Brenner

We could also overlay the different type of forests in and around this bird’s home range in order to get a better sense of the immediate landscapes around towhees.

ForestClass.png

As in most research, if we can gather similar data and create home ranges for a larger sample of towhees, we can more confidently use this data to answer some really interesting questions about our ecosystem. Think of the possibilities!

-Does proximity to developed areas or edges influence survival?

-Do females use more or less space, or do birds with our without young use more or less space?

-Does distance to other managed forests impact spatial movements?

The possibilities are endless! These are the types of questions I’ve been working on with these little songbirds, and with a rapid increase in tracking technologies, all sorts of spatial questions are starting to be answered and will be addressed in the near future. But a home range is always a good place to start!

(All maps were created with ArGis.)

 

About the author:
Steve Brenner studies the impacts of habitat management on avian spatial ecology in the Scott McWilliams lab at the University of Rhode Island

steve
 

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Bring on Spring! Animal physiology is as transformative as our seasons

Physiology is the study of how animals work and perform everyday functions like breathing, walking, and maintaining a normal body temperature. In many species, animal physiology responds to environmental conditions including the amount of available water, the temperature, and the time of year. A general rule is that when the environment changes then animal physiology responds.

It is important to note that changes in physiology and behavior often occur together. For example, a bird readying itself for migration will eat a larger amount of food in order to double the size of their fat stores that are crucial for providing fuel during long-distance flight. This behavior would be impossible if their physiology was inflexible, but luckily they remodel their digestive system to cope with processing all of this food.

An alternative tactic that animals use to fit into their environment is that they change only their behavior so that they experience a constant set of environmental conditions, and as a result they avoid changes in their physiology. Aquatic turtles use this strategy to keep their body temperatures fairly constant by switching between basking themselves in the hot sun and plunging themselves in the cooler water.

Whether or not animals change their physiology, their behavior, or their physiology and behavior depends on the species and on their environmental situation. For this post I'll summarize the types of changes in physiology that this blog will focus on.

An unfrozen wood frog ( Rana sylvatica ) found by a biology undergraduate student in Massachusetts, September 2017,  Photo credit: Kristen DeMoranville

An unfrozen wood frog (Rana sylvatica) found by a biology undergraduate student in Massachusetts, September 2017, Photo credit: Kristen DeMoranville

Physiology can change on a short-term timescale soon after their environments have changed, and these changes are reversible. This happens to us. Standing outside on a cold winter day in thin mittens, it only takes about 30 minutes to notice our hands are cold and beginning to hurt. In this situation, our blood flow has been rerouted to our center to keep our important organs warm. During the winter in North America a specific species of frog, the wood frog (Rana sylvatica), buries themselves beneath the soil in preparation for freezing temperatures. These frogs are unable to keep their body temperatures high enough so that their organ systems could properly function. These frogs embrace that shortcoming and allow their bodies to freeze nearly solid immediately as ice forms around them in order to survive the cold. Special physiological adaptations protect their organs during this freeze and help them to completely recover as soon as the temperatures warm and ice disappears.  The Dr. Richard Lee & Dr. Jon Constanzo lab investigates the physiology of these amazing frogs. An overview of Dr. Lee & Constanzo's research can be found here.
Spring is here and wood frogs are emerging from their frogsicle forms NOW! If you are in Canada or eastern North America then keep your eyes peeled and ears open.

A banded male North American cardinal ( Cardinalis cardinalis ) in Rhode Island, April 2018,  Photo credit: Steve Brenner

A banded male North American cardinal (Cardinalis cardinalis) in Rhode Island, April 2018, Photo credit: Steve Brenner

Animal physiology can change on a long-term scale either days, weeks, or months after their environments have changed, and these changes are reversible. We can relate to this too. Taking a long walk on the first scorching day of the summer we feel drained. After experiencing this heat day after day it seems easier to take this same walk in mid-summer. Our bodies adjust to the heat with repeated exposure, and as a result we can better endure hot weather. Songbirds that stick around for cold winters rather than migrate to tropical regions have to change their physiology so that they can stay warm enough to properly function and survive. Winter resident birds like the Northern Cardinal (Cardinalis cardinalis) keep warm by enhancing their ability to generate heat through a tactic similar to mammalian shivering, but without the muscle trembling that we experience. They also increase their fat and feather layers in the winter to improve insulation which is crucial for keeping that extra heat that they produce inside their bodies. These physiological adjustments do not happen after the first freeze or even with the first snowfall, rather it takes weeks at cold temperatures for birds to transform their bodies into fat, fluffy, heat generating machines. The Audubon society covers how birds stay warm in more detail here and Dr. David Swanson's lab focuses much of their research on cold hardiness.
Spring is here, and despite the recent snow, cold hardy birds like the Northern Cardinal and Black-capped Chickadee (Poecile atricapillus) are losing fat and shedding fluffy feathers in preparation for the breeding season.

 
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A hibernating 13-lined ground squirrel (Ictidomys tridecemlineatus) in Dr. Jim Staples lab at the University of Western Ontario, December 2015, Photo credit: Kristen DeMoranville

Animal physiology changes in repeating patterns either daily, monthly, or yearly under the control of an animal's internal biological clock (defined as the bodily components that keep track of time within an animal). Whether you are a night owl or an early bird, our nightly sleep habits are controlled by our biological clocks. Read more about how our biological clocks control sleep here
Mammals like the 13-lined ground squirrel (Ictidomys tridecemlineatus) are adapted to hibernate during harsh winters when temperatures are below freezing, days are short, and food is unavailable. The internal clocks of these mammals filter through the environmental cues (e.g., temperature, light levels, and food availability) to control physiology and make hibernation possible. Ground squirrels lower their body temperature (and actually feel cold to the touch! See above picture) and slow their metabolism* (defined below) so that they are barely using or producing any energy. This means that their heart rates drop from 200 beats per minute to 20 beats per minute. Their biological clocks use similar environmental cues to stimulate their metabolism and rouse them from hibernation. National Geographic gives more overview about hibernation here, and Dr. Jim Staples investigates the metabolism of hibernating ground squirrels.
The onset of Spring is inciting hearts to flutter and, as Owl would explain to Bambi and Thumper, squirrels are twiterpated. If you live central North America then go searching, and don't forget to count their lines.

Animal physiology responds to environmental changes either on a short-term scale, long-term scale, or periodically in a repeating pattern. These changes in physiology can be difficult to observe firsthand. Although, behavioral changes can often act as a flag that alerts us to unnoticeable changes within an organism. Next time that you observe a behavioral change in one of your favorite critters I challenge you to think about the types of physiological adjustments that your animal might require to make that behavioral change possible.

*Metabolism is a concept we will continue to revisit. This is how I like to think of the concept: All organisms require energy to perform their daily activities, and this so called fire for life is the product of chemical processes collectively referred to as an organism's metabolism.

 

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About the author:
Kristen J. DeMoranville @Kris10DeMo is a Ph.D. student researching the effects of diet and long-distance flight on a migratory songbird in Scott McWilliams lab at the University of Rhode Island

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