Research

I have many research interests, although I consider myself an animal ecologist, with a strong emphasis on all things physiological. My work straddles the disciplines of physiology, disease ecology, parasitology, hematology, and natural history. The majority of this work involves studying how animals' physiologies respond to their environments, and most of my previous and current projects address issues related to this subject (although I am not averse to the occasional natural history note or techniques paper). As examples, my work involves understanding how diseases affect immune function, how environmental variation affects pigmentation production, and how stress induces developmental instability. Furthermore, this work is not limited to any one taxon, but spans the disciplines of ornithology, entomology and herpetology. For example, the following pictures represent some of the many species I am currently or have previously worked on, either for my own research or through collaborations:

More specific projects I have been or am currently involved with are listed below

 

1) Examining hematological responses to natural and anthropogenic stressors in amphibians

This topic was the focus of my doctoral research in the Maerz lab at UGA, which included a number of projects aimed at understanding the relationships between environmental quality and aspects of amphibian 'health' - especially stress. Specifically, I examined the stress response of a number of amphibian species with respect to breeding, captivity, disease, rearing density, and several other stimuli. Moreover, I measured stress using a 'non-conventional' method involving counts of white blood cells. This methodology is based on the idea that increases in stress hormones lead to characteristic changes in white blood cell populations and by identifying these changes, stress can be inferred. For more info on this topic, see the review paper I co-wrote here.

 

2) Using computer-assisted measures of color and symmetry to assess animal fitness

I am very interested in using computer-assisted digital technology to assess the health and fitness of a range of animals by measuring features of their morphology. Questions I ask include what factors influence melanism levels in organisms such as monarch butterflies, or diamondback terrapins? Why are some house finches more brightly colored than others, and is it a signal of fitness? How does infection influence the expression of color in finches? Does spot symmetry signal health in spotted salamanders? During this research I have gathered several digital photo libraries of amphibians, turtles, insects and birds which I am analysing with these techniques, and some of these libraries can be seen here. These have been gathered by myself or my collaborators which include Kristine Grayson, at the University of Virginia, Brian Todd, formerly of the Savannah River Ecology Lab, Andrew Grosse, at the University of Georgia, and Sonia Altizer, my wife!

Below are examples of some of the image libraries I've worked on. Click thumbnail to view the library.

Diamondback Terrapins
Milkweed Bug Wings
Male House Finches
Marbled Salamanders



3) Understanding the links between red and white blood cells and animal fitness

In vertebrate animals, white blood cells make up the primary line of defence against infections with pathogens, so it is obvious that they should serve as indicators of health in the animal. However, many questions remain unanswered regarding which white blood cells respond to the range of infection types, or how the function and morphology of these cells change with infection. There are also many questions regarding red blood cells, especially their morphology, that I am exploring, to see how they relate to animal health and fitness. In these investigations I use a combination of traditional hematological techniques and novel image analysis methods to quantify red cell dimensions. I have also recently started a website to aid researchers who study leukocytes of non-mammals, the Wildlife Leukocytes Website.

 

4) Effects of diseases on animal physiologies

While I do not consider myself a true disease ecologist, I have studied various diseases in animals as part of my work. In most cases I am really interested in learning how the disease alters leukocyte numbers or other aspects of health. One project examined how infection with the bacteria Mycoplasma gallisepticum (MG) in house finches affects leukocyte numbers. I have also been involved with studies of amphibian diseases, such as a novel protozoan pathogen infecting frogs in local ponds, as well as chytridiomycosis in bullfrogs. Finally, blood parasite infections is also one of my interests.

House finch infected with MG
Unnamed protozoan in leopard frog larvae
Blood parasite in avian blood smear

       

5) Monarch Butterflies: morphological correlates of fitness

I am currently working on several onging projects comparing morphological traits among populations and individual monarch butterflies. Within these projects, I am particularly interested in developing novel methods of data collection using new digital technology. For one particular project, we used image analysis to make fine-scale detailed comparisons of monarch forewings between several populations. In another, we compared wing melanism between eastern, western and South Florida monarch populations. I have also collaborated with other researchers on projects examining how wing color patterns in monarch butterflies influence mating success, and I recently described an unusual pattern where migratory monarchs appear to have redder wings than non-migrants!

 

6) Migration of Monarch Butterflies

Although this subject is not neccessarily related to ecophysiology, it is of interest to me because of my background in bird migration (below). Monarch and bird migrations have many parallels, and much of my monarch migration research has beeen with this in mind. Further, most of this work involves analysing existing data sets from monarch migration censuses and population monitoring programs. Because of this work, I am now a member of the steering committee for the North American Network of Monarch Monitoring Programs, or MonarchNet, which has a website here.

 

7) Stopover ecology of migratory landbirds

This was the topic of my master's thesis at Acadia University, and one that I still am interested in. For my thesis project, I assessed lengths of stopover and rates of fat deposition of landbirds at a fall migratory stopover site in southern Nova Scotia. One species in particular was of interest to me, the Blackpoll Warbler, which makes a non-stop, transoceanic flight to its wintering grounds, as opposed to most migrants, which make frequent stops. A pdf copy of my thesis can be viewed here from the National Library of Canada. While conducting this research, I also initiated my first study of hippoboscid flies, which are ectoparasites of birds, and I continue to study these fascinating parasites.