Snake Conservation a Slippery Feat

Elusive and reclusive, they slither swiftly and silently through the undergrowth, virtually undetectable thanks to a low profile and clever camouflage. For Environment Canada scientists and others involved in snake research and recovery programs, the challenges lie not only in the difficulties of studying these cryptic creatures, but also in the battle against negative public perception.

Although rattlesnakes are the only venomous species in Canada, the fact of the matter is that many people don't like snakes—whether they're harmless or not. In fact, one of the reasons there are 10 species of snakes at risk in Canada is that most have been, and in many cases still are, persecuted by humans. The results of a recent survey of 2 000 Canadian and American students-presented at a symposium of the Canadian Amphibian and Reptile Conservation Network in Quebec City this October- showed that people develop an aversion to snakes at a young age.

Attempting to recover declining populations, therefore, means spending a great deal of time on public awareness and education aimed at cultivating an appreciation for the value of snakes and their roles in functioning ecosystems, and explaining that the gut reaction most people have toward snakes is likely a simple precautionary response retained from our evolutionary ancestors.

Even venomous species, like the threatened eastern massasauga rattlesnake, use their poison primarily for prey acquisition, and only secondarily for defence. To quell fears among people who live and work within its range—limited in Canada to Ontario's Georgian Bay and Bruce Peninsula regions and isolated populations in the Niagara Peninsula and the Windsor prairies—the massasauga recovery team has hosted numerous workshops and presentations instructing people on how to live safely with rattlesnakes in their environment. Although there is a lack of empirical evidence concerning the effectiveness of such initiatives, the steady increase in the number of massasauga sightings reported in recent years suggests that the more good information people have about these animals, the less they perceive them as a threat.

Development and land-use activities, however, remain the primary factors responsible for declining snake populations. In addition to causing direct deaths on roads, agricultural lands and residential properties, human activity and land conversion have greatly reduced and fragmented snake habitats, isolating populations and making them highly vulnerable to local extinction as a result. Yet learning more about their habitat needs has not been an easy chore, as snakes prefer to stay out of sight, are generally hard to locate and capture, and are therefore difficult to study—even in areas where they are plentiful. As such, traditional studies often yielded biased insights because they typically provided data only when and where biologists could actually observe snakes, and no information on snakes when they were out of sight.

It wasn't until the advent of small, temperature-sensitive, implantable radio transmitters that biologists were able to build up a bank of unbiased information on the activity patterns, habitat use, and thermal ecology of snakes. Among other things, they learned that snakes make more use of specific habitats, like forest edges, farmland hedgerows and hollow trees, than was previously thought. In addition, their choice of precise habitats is often driven by behavioural thermo-regulation, whereby they shuttle back and forth between different thermal environments in order to moderate their body temperature to facilitate their activity needs. Over time these data have revealed that selection of fine-scale micro-habitats within larger habitat contexts is of critical importance to snakes because they serve a variety of highly specific purposes—from prey acquisition and digestion to embryo development and hibernation.

Canada's largest snake—reaching lengths of up to 2.5 metres—the black rat snake is an excellent and frequent climber that generally inhabits upland areas.

Another useful advance in ecological studies of snakes has been the use of passive integrated transponders, or PIT tags, to mark individuals and enumerate populations. PIT tags are inert glass beads, about the size of a grain of rice, that carry unique alphanumeric codes and are injected as permanent markers under the skin of a snake. These tags can be read in the field with a portable scanner, the identities of recaptured snakes being automatically stored, and later uploaded for use in demographic analyses. This simple technique is a vast improvement over previous external marking methods, which tended to fade and become indistinct over time. By using PIT tags, snake ecologists now have an unambiguous and highly efficient tool for quantifying large populations—a task that is particularly labour-intensive when working on communally hibernating species where numbers can exceed 100 snakes in a single underground den.

Maps of Ontario, British Columbia, and Saskatchewan showing the approximate ranges of the 10 snake species that are at risk in Canada.

The most recent contribution to snake conservation comes from analyses of DNA and the quantification of the genetic population structure of snakes—a measure of how wild populations are organized and interact with one another. Canadian ecologists are responsible for the development of some of the first microsatellite genetic markers for snakes, in particular those used to carry out applied research on both the massasauga and the black rat snake—Canada's largest species, which often exceeds 1.3 metres in length. The reduction of deciduous forest has eliminated most of the black rat snake's original range, and this threatened species is now found in limited numbers only in the Carolinian forest region of southwestern Ontario and southeastern Ontario's Frontenac Axis.

To date these analyses have shown that black rat snakes have relatively large genetic neighbourhoods, with clusters of hibernating populations exhibiting little genetic differentiation. Massasaugas, in comparison, occupy extremely narrow genetic neighbourhoods—with a high degree of divergence between neighbouring populations living in relatively close proximity. This knowledge of the extreme genetic structure found in massasaugas has precipitated a new perspective on the species that has implications for the future direction of recovery and management. Among other things, the data suggest that while massasaugas may, in a sense, be genetically preadapted to living with relatively limited gene flow, they are also unlikely to naturally recolonize localities from which they have disappeared.

All of these tools are being used to gather baseline information on a small, isolated population of massasaugas persisting on a 230-hectare parcel of tallgrass prairie in Windsor, Ontario. In this case, the recovery team is using research evidence to assess the long-term viability of a population of snakes living in the very midst of an urban residential community, on land currently zoned for development. In a bid to recover this highly jeopardized population, the recovery team is drawing on insights from a variety of research perspectives, including behavioural ecology, vegetation management, conservation genetics, and land-use planning. In order to make ecologically informed decisions about the future management of the population, the team is selecting from among a host of recovery options that range from in situ land stewardship to captive breeding and repatriation.

Last summer marked the start of an innovative snake recovery project that takes a "coarse-scale" e cosystem approach to the conservation of three species at risk on Pelee Island, in western Lake Erie. The project combines public awareness, community involvement, field ecology, ecotoxicology, genetic research, and geographic information system (GIS) mapping on the Lake Erie water snake, eastern fox snake and the blue racer snake, as well as assessments of the impacts of land-use planning and human activity on these species.

Found on only a handful of islands stretching between Point Pelee, Ontario, and Sandusky, Ohio, the endangered Lake Erie water snake is estimated to number fewer than 1 000 adults. An inhabitant of rocky shorelines, where it forages for fish and other aquatic prey, it is strongly affected by coastal development and is vulnerable to genetic swamping by the emigration of individuals from mainland subspecies. Studies of habitat use, availability, and the impact of toxic contaminants on this species are a major focus of the project being coordinated by the University of Guelph and the Canadian Wildlife Service.

The global distribution of the threatened eastern fox snake is restricted to the Lake Huron-Lake Erie waterway shoreline, adjacent tributaries and islands, where it inhabits primarily unforested, terrestrial shoreline ecosystems adjacent to marshes. The fact that this is one of the most seriously threatened natural regions of Canada and that 65-70% of the subspecies range is in Ontario lends particular importance to conservation efforts north of the Canadian/American border. To help the fox snake cope with declines in habitat quality and quantity, research biologists are mapping the movements and critical habitats of the island population and overlaying them with human activity and development patterns to identify areas of conflict and potential solutions. Furthermore, the team on Pelee Island has initiated the construction of artificial nesting and hibernation sites on protected lands—the former hollow logs filled with nesting material and shell remnants and the latter large excavated holes filled with loose material, such as rocks and sand.

Similar experimental efforts are being directed at the endangered blue racer, another communal nester and hibernator. Found in Canada only on Pelee Island, where its numbers are estimated at some 200 adults, the racer prefers savannah, prairie, and pasture habitats, and is negatively affected by certain agricultural practices and land conversion in general. Efforts to restore this species have also included the planting of hedgerows to provide safe movement corridors, prescribed burns to maintain open vegetation communities, and public outreach programs aimed at encouraging stewardship and the restoration of natural landscapes.

Despite the progress made toward conserving snakes in Canada over the past decade, much remains to be done for species currently at risk, as well as those approaching that status. By taking into consideration the impact and interaction of human activities on a suite of species across the landscape, the Pelee Island project serves as a model approach for future research—one that includes perspectives and skills from a wide range of disciplines and sectors, including educators, field biologists, planners, GIS technicians, government officials, molecular ecologists and local citizens. Its example could well hold the key to the success of future efforts to save these fascinating and ecologically mysterious creatures.

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