Academics

Funding source: NSF, Cross-Disciplinary Research at Undergraduate Institutions Program (Continuing Grant, 2005-2009)
Primary collaborators: Drs. Rich April (Colgate Geology), Randy Fuller (Colgate Biology), and Michele Hluchy (Alfred University Environmental Studies)
Colgate students involved: Jake Krong ’06, Jose Medina ’07

Along with collaborators, I am attempting to better understand the adverse consequences of acid deposition in the Adirondack Mountains, a region that is particularly sensitive to this effect of air pollution. My work focuses in terrestrial ecosystems and seeks to elucidate the connections among acid deposition, calcium depletion, and animal populations (Figure 1).

As acid deposition, which includes acidic rain and other forms of precipitation, percolates through forest soil, hydrogen ions displace other positively charged ions, such as calcium, which then tend to be lost from the biologically active upper soil layers. Calcium is an essential plant and animal nutrient. Thus, calcium depletion represents a potential mechanism by which acid deposition can harm organisms. Longstanding work in northern Europe and recent work in North America have established links among acid deposition, calcium depletion, and reproductive decline of birds. Birds have high calcium requirements during egg formation. Similarly, mammals have high calcium requirements during reproduction. However, no one has examined the possibility that mammals might be affected by acid-induced calcium loss. I am studying shrews, which are insectivorous mammals in the family Soricidae (shrew web site), and their invertebrate prey in habitats with varying amounts of available calcium and in calcium-depleted habitats following calcium amendment.

Invasion of North America by European Buckthorn (Rhamnus cathartica) [project web site]

Funding source: NSF, Research at Undergraduate Institutions Program (Continuing Grant, 2001-2005)
Primary collaborator: Dr. Deanna McCay (Colgate Geography)
Colgate students involved: Anthony Caragiulo ’03, Jessica Czaka ’08, Matthew Feldman ’06, Amitabha Gupta ’05, Jennifer Hild ’03, Dave Hosford ’05, Elizabeth Juers ’08, Toby Mandel ’03, Casey Pierce ’05, Dave Rozolsky ’06, Amirah Shahid ’05, Brendan Smith ’02, Daniel Starobin ’03, Abby Webb ‘04

The invasion of new habitats by exotic species represents one of the most pressing environmental issues of our time. However, there is much about the invasion process that is still unknown. Our ability to predict which species will be successful in which habitats, for example, is very weak. This is because the success of an exotic species is the result of a complex interaction between the invading species and the invaded community. Through the current work, my collaborator and I seek to better understand why an invasive exotic plant in our area, European buckthorn, is successful in some habitats and unsuccessful in others. Our project was set within three habitats common in our fragmented landscape: sugar maple forests, abandoned agricultural fields (old fields), and conifer plantations. My strongest area of interest in this project is the role that vertebrate animals, including mammals, play in facilitating or inhibiting invasion in different environments.

The project has three components. First, we have been describing the demography and spatial distribution of buckthorn individuals at local (< 1 hectare) scales using survey equipment and a geographic information system. Second, we dissected the invasion process into a series of processes (Figure 2), which are necessary for successful invasion, and examined each processes experimentally. Finally, we combined our results at the local scale with habitat maps of Madison County to better understand how this invasive plant might move among areas in a larger landscape.

Overall, our work has supported the notion that the invasion process is highly dependent on ecological context. In maple forests, there are relatively few young buckthorn individuals, which are concentrated near openings in the tree canopy (e.g., trails). In abandoned agricultural fields, many buckthorn seedlings are strongly concentrated near large seed sources (reproductive female plants). In coniferous plantations, many buckthorn individuals of various ages are equitably distributed throughout the forest. Perhaps the most striking conclusion of our survey work has been that conifer plantations, which are very common in New York State, seem to be highly invasible by exotic species.

Based on the results of our surveys, we formulated a series of predictions that we were able to test experimentally. Because these experiments were manipulative, they gave us greater power to understand the mechanisms underlying the pattern we saw under natural conditions. We found that buckthorn plants in old fields allocate a much greater portion of available energy to reproduction and produce many more viable seeds than plants in forests. Because seeds are generally dispersed close to parent plants, this leads to many more buckthorn seeds in old fields compared to other habitats. Seeds were more likely to be eaten in forests than in old fields due to habitat preferences of small mammals, which are the primary seed predators in our area. Survival of seedlings is low in mature forests, due to inadequate sunlight, and low in old fields, due to competition with grasses, compared to plantations. Finally, buckthorn plants in old fields attain reproductive maturity more quickly than plants grown in forests. Thus, buckthorn seems to be prevented from successfully invading mature forests by a combination of low seed rain, high seed predation, low levels of sunlight, and slow growth to maturity. Plantations are heavily invaded because levels of sunlight, which are intermediate between sugar maple forests and oldfields, are adequate for greater survival than maple forests but do not allow the growth of grasses, which can competitively exclude buckthorn.

The third portion of the project involved landscape-level pattern of invasion by buckthorn. Here we aimed to apply our local findings across the broader landscape of the region. We used a geographic information system and digital aerial photographs to quantify the habitats in the Towns of Hamilton, Madison, and Brookfield of Madison County. We then sampled 100 points randomly placed within the landscape for buckthorn and looked for associations between the presence of buckthorn and various environmental factors, including light levels and habitat type. We found that the landscape of our study area was largely forested (37%), with 6% of the landscape in conifer plantations. Agricultural lands covered 20% of the region, and abandoned old fields covered 17%. The remainder of the area is in wetland, residential, and commercial habitats. Among the points surveyed, presence of buckthorn was primarily found in old field and plantation habitats. When buckthorn was found in forests, it was positively associated with light availability. That is, buckthorn was typically found in open, relatively young forests. Proximity to agricultural land was also important, which suggested that agricultural edges and fencerows may aid in dispersal of this species in the landscape.

Ecological Role of Dead Wood in Southeastern Forests

Funding source: U.S.D.A. Forest Service, Contractual Agreements (no active awards)
Primary collaborators: Dr. W. Mark Ford (U.S.D.A. Forest Service), Mr. Mark Komoroski (Savannah River Ecology Laboratory)
Colgate students involved: Matthew Behum ’02, Angela Brandt ’03, Sara Cavin (transfer), Meredith McLean ’02

The aim of this research has been to better understand the importance of dead wood to small mammals and other animals in managed southeastern pine forests. Dead wood is often removed as part of forest management in the southeast. Despite this fact, we know practically nothing about what effect this removal is having on animals. The general approach has been two-fold. First, we have sampled animals at areas from which large (> 10 cm diameter) logs have been experimentally removed and areas from which logs have not been removed. Secondly, we have examined the fine-scale movement of animals to determine the ways in which they use dead wood and the extent to which it is used.

The main conclusion of this effort has been that dead wood is an important resource for many species in the southeast. The cotton mouse, for example, extensively uses dead wood, particularly as dens (McCay, 2000). This project was the first to point to the importance of decomposing stumps as habitat for forest animals. Cotton mice use logs as a means of navigating through their habitats. Dead wood also is important to shrews, including the very uncommon least shrew (McCay and Komoroski, 2004). We demonstrated negative demographic effects of log removal on the least shrew and the southern short-tailed shrew. These results have implications for the ways that land managers practice forest management. For example, certain methods used when preparing a site for the replanting of trees allow retention of old stumps. These data suggest that those methods might improve the future quality of the environment for cotton mice and, perhaps, other species. Similarly, certain “sloppy” methods of timbering allow the retention of more logs than “clean” methods. Increasing logs available for animals can increase the quality of the environment for certain species.

Sexual Size Dimorphism and Rensch’s Rule in the Shrews

Funding source: None
Primary collaborator: Dr. Howard Whidden (East Stroudsburg University)
Colgate students involved: None to date

Sex-based size dimorphism (SSD) is relatively common among animals. Indeed, humans provide an example of male-biased SSD. It is widely believed that shrews exhibit no significant SSD; however, this perception is based on detailed knowledge of only a few North American and British shrew species. A collaborator and I are undertaking a review of SSD in the shrews and are examining some of the less-well-known African and Asian shrews.

Contrary to initial expectations, we found evidence for strong SSD in several shrew species. Interestingly, male-biased SSD was greatest in large, primarily African and Asian, shrews; whereas, female-biased SSD was present in some of the smallest shrews (Figure 3).

The evolutionary forces leading to SSD are complicated but largely fall into two categories, fecundity selection and sexual selection. Fecundity selection is based on the physiological constraints of females. Larger females can produce more offspring, so there should be selection for females to be big. Sexual selection is based on factors that cause females to mate with particular males rather than others. Size gives males an advantage in these interactions, so there should be selection for males to be big. Generally, small species tend to be more influenced by fecundity selection; whereas, large species are more influenced by sexual selection. This phenomenon is known as Rensch’s Rule. This rule partly explains the observation that many small invertebrate species include large females and small males; whereas, many large mammal species include small females and large males.

Only in the hummingbirds has it been documented that both female-biased and male-biased SSD exists within the same taxonomic family. Thus, shrews apparently exhibit an uncommon pattern among animals. Interestingly, hummingbirds are physiologically similar to shrews; both have high metabolic rates and live short lives. Learning more about the factors leading to SSD in shrews can help us to better understand Rench’s Rule and the trade-off between fecundity and sexual selection in animals.

Community Ecology of Shrews in the North America

Funding source: None
Primary collaborators: Drs. W. Mark Ford (U.S.D.A. Forest Service), Matthew Lovallo (Pennsylvania Game Commission), and Peter Scull (Colgate Geography)
Colgate students involved: Jessie Berman ‘04

The aims of this work are to determine what environmental factors affect the diversity of shrews in different habitats and, more generally, to aid in our knowledge of how similar shrew species coexist within multi-species communities. Our basic approach has been to work with pre-exiting field data to analyze spatial distributions. Further, we have correlated environmental data with shrew distribution patterns. The majority of this work has focused on the southern Appalachians, where shrews are more diverse than virtually any other place on Earth.

Our work has underscored the importance of environmental moisture and forest type as factors affecting shrew diversity. Shrews are very sensitive to environmental moisture because of their high metabolic rates, and this physiological constraint seems to limit abundance and diversity of shrew communities (Berman et al., in review). Shrews are strongly affected by forest type along moisture and elevation gradients (Laerm et al., 2000; Ford et al., in press); however, shrews are relatively insensitive to low-intensity forest harvesting (Ford et al., 2000; Menzel et al., 2005). Interestingly, we found that shrews of similar size are less likely to be found in the same habitats (McCay et al., 2004). For example, the masked shrew and the southeastern shrew are very similar in size. In the southern Appalachians, the masked shrew is found at high elevations (> approx. 800 meters); whereas, the southeastern shrew is found at lower elevations (Ford et al., 2001). Using computer simulations we determined that the structure of shrew communities in the southern Appalachians was largely due to spatial pattern of geographic ranges, rather than current competition among species (McCay et al., 2004).

Behavior of the Northern Short-tailed Shrew (Blarina brevicauda)

External funding source: None
Primary collaborators: None
Colgate students involved: Angela Brandt ’03, Laura Chadderdon ’05, Matt Drew ’05, Eva Dettweiller Robinson ’05, Elizabeth Wolyniak ‘05

In collaboration with Angela Brandt '03 and Eva Robinson '05, I have been examining the factors affecting the activity patterns of northern short-tailed shrews. Shrews have very unusual patterns of activity among mammals. They are active throughout the day and night, resting 15-30 minutes every two hours or so. The environmental factors leading to the evolution of this pattern of activity are unclear. Thus, we subjected shrews to various temperature, photoperiod, and humidity treatments in the lab and measured their pattern of activity using chambers armed with light-beam circuits. Results of this research suggest that the activity patterns of shrews are highly insensitive to short-term variation in environmental conditions (Brandt and McCay, 2004; Robinson, in review), contrary to the results of less well-controlled experiments. Thus, we believe that previous results have been clouded by certain behaviors, including hoarding and burrowing, that we were able to control in our study.

Students and I have also been radio-tracking short-tailed shrews to better understand their behaviors in the field. What we know about the behavior of wild shrews has largely come from trapping data, which can be biased by the response of animals to traps. Radio-telemetry allows the unobstructed observation of animals in nature. Small radio-transmitters are implanted into the abdominal cavities of shrews, which can then be tracked using signal receiving equipment. During the past two years I have been trained by Colgate’s consulting veterinarian, Dr. Frank Martorana, to perform implantation surgery, and we have begun the tracking of implanted shrews. Preliminary results suggest strong use of dead wood and primarily nocturnal movement outside of borrows.

I am a member of the following professional organizations: Sigma Xi, The American Society of Mammalogists, The Wildlife Society, and the Invasive Plant Council of New York. I have served as the advisor of our local chapter of Beta Beta Beta and am an honorary member of Phi Eta Sigma. I am a Certified Wildlife Biologist.

Conservation Biology (BIOL 330) is a study of biological diversity on Earth and the mechanisms that can be used to preserve it. Our approach is hierarchical, ranging from genetic through ecosystem diversity.

In Comparative Environmental Physiology (BIOL 311), I place the physiological adaptations of vertebrate animals within an evolutionary and ecological context. In short, we study "how animals work" and strive to understand why they work differently in different environments.

Investigations in Vertebrate Ecology (BIOL 488) is a research tutorial focusing on the study of vertebrate animals in natural environments. The nature of the course varies according to the interests and abilities of students, but typically focuses on the movements and population dynamics of small vertebrates in central New York.

Conserving Nature (CORE 107) is a Scientific Perspectives course focusing on the science and ethics of natural-resource conservation.

• Brandt, A.J., and T.S. McCay. 2005. Temperature and photoperiod effects on activity of the northern short-tailed shrew (Blarina brevicauda). Bios 76: 9-14.
• McLean, M.L., T.S. McCay, and M.J. Lovallo. 2005. Influence of age, sex, and time of year on diet of the bobcat (Lynx rufus) in Pennsylvania. American Midland Naturalist 153:450-453. [PDF]
• McCay, T.S., M.J. Lovallo, W.M. Ford, and M.A. Menzel. 2004. Assembly rules for North American shrew communities: Influence of geographic range and habitat partitioning. Oikos 107:141-147. [PDF]
• McCay, T.S., and M.J. Komoroski. 2004. Demographic responses of shrews to removal of coarse woody debris in a managed pine forest. Forest Ecology and Management 189:387-395. PDF
• McCay, T. S. 2001. Blarina carolinensis. Mammalian Species 674:1-7. [PDF]
• McCay, T. S. 2000. Use of woody debris by the cotton mouse (Peromyscus gossypinus) in southeastern pine forests. Journal of Mammalogy 81:527-535. [PDF]