By Leslie Anthony.
One cold Boxing Day, James Baxter-Gilbert and Julia Riley hopped in their car and drove to the remote east side of Algonquin Park. Baxter-Gilbert donned an orange emergency flotation suit – the kind carried on fishing boats – attached a rope to himself, tied it off on a tree, and walked out on a frozen bay. Playing the rope, Riley watched calmly as he promptly fell through up to his waist. “You OK?” she called. “Yeah,” he replied, clawing his way back onto solid ice only to walk ten steps and fall through again. The comic leitmotif repeated as Baxter-Gilbert alternately cut holes in the ice with an auger and his own weight.
Were they scouting ice-fishing hotspots? Training for winter search-and-rescue? Not quite. This unlikely vignette is the face of turtle conservation in the Great White North, and the pair likely weren’t the only herpetologists (those who study reptiles and amphibians) so engaged that day: most who conduct field research on these familiar log-lounging icons of summertime eventually find themselves scouting their subjects through a blanket of snow and ice.
“You can’t say you’re a Canadian herpetologist until you’ve done winter work,” laughs Riley, who relishes the paradox of searching out coldblooded animals in a frozen landscape.
Indeed the outing – where they’d measured dissolved oxygen (DO) at hibernation sites – was no anomaly. Between them, the two species-at-risk researchers have worked on seven of Canada’s eight native freshwater turtles: Blanding’s, map, musk, painted, snapping, spotted and wood. Each were conservation efforts that involved tracking turtles via radio telemetry, and most included winter work. Why the brumal preoccupation?
“We’re at the northern limits in Ontario for most of these species, so time spent overwintering represents at least half their lives,” says Canada’s top turtle researcher, Dr. Jacqueline Litzgus of Laurentian University. “What happens in summer with food and growth is important to fitness and breeding, but if you can’t survive winter your fitness is zero.”
As such, turtles’ long annual nap at the bottom of ponds, lakes and rivers has become a focus of conservation efforts in eastern Canada. Because site choice is very particular and vulnerability high during this time, the loss of – or impact to – overwintering habitat can quickly override other considerations in the demise of a population. But this knowledge is cold comfort if it can’t be quickly applied to conservation. And, unfortunately for a group that first appears in the fossil record some 220 million years ago and has changed little since, it’s a race against time.
Turtles are in troubled waters worldwide, but very much so in Canada, where most species already eke out a marginal existence. Habitat fragmentation, degradation and loss from road, agriculture and urban development have further isolated many in small-population pockets; they’re not going anywhere fast, and they’re not doing well. Nearly all our turtle species show significant declines in absolute numbers and viable populations, a problem exacerbated by government foot-dragging. (There are more formal turtle-recovery teams in Ontario than there are species, but while declines continue in hare-like leaps and bounds, protection moves at the speed of, well… a tortoise.) The problems start with basic biology: all turtles are long-lived and slow growing, with late sexual maturity (at 10-30 years) and a long reproductive life (up to 50 years).
Ecologically, these traits balance the high number of eggs and hatchings lost to predation, evolving in concert with low adult mortality. While this has allowed turtles to survive cataclysmic events in Earth’s history, populations of animals with such characteristics cannot quickly replace losses after sudden episodes of high adult mortality. Despite their geological resilience, turtles aren’t equipped to deal with the myriad anthropogenic threats of their active season—high road mortality (while moving to and from nesting or overwintering sites) and overharvesting for the food or pet trades. Far from a respite, the inactive winter season also presents a range of threats. Turtles face three major challenges to overwintering survival: freezing, predation, and acidosis (the toxic accumulation of metabolic lactic acid in tissues).
Study after study has demonstrated how turtles select hibernation sites which minimize these threats. Thermal stability is key. “A certain depth of water and a certain configuration that maintains temperatures in that layer is required—maybe a hole or a spring,” says Litzgus. “It’s very specific.”
Not knowing the preferred sites for populations at risk presents a significant conservation problem. Construction companies, for example, often use winter for particular types of work because it’s easier to drive heavy equipment across frozen soil and wetlands. This presents more of a hazard than just accidentally crushing snoozing turtles. “[Some species] choose the coldest areas of stratified water, so the biggest threat during hibernation becomes changes in hydrology,” notes Litzgus with concern. “Any alterations to water flow will change the thermal profile available to turtles—which in turn can increase risk of acidosis or predation.”
With good sites at a premium, many turtles often end up hibernating together in the same place. The importance of such communal hibernacula to springtime mating—well understood in wide-ranging animals like snakes—is now also apparent for turtles. Because a large percentage of the breeding population is potentially present in one small area, the population effects from destroying the site or its occupants can be disastrous. With it so easy to perturb the critical overwintering habitat of turtles, the only thing between extirpation and conservation may be those willing to brave the cold on their behalf. But it doesn’t always mean tying yourself to a tree.
“Wood turtles need wiggly, fast-flowing rivers with cobble or sand bottoms and sandbanks at the bends,” says Litzgus. “These rivers are easy to identify on a map, but since logging changes hydrology and siltation in some stretches, overwintering sites are often in remote areas that are dangerous and physically challenging to get to.” Wood turtles’ preferred place to hibernate is a metre deep and a metre from the bank. If there’s a thaw where ice pulls off the shore then refreezes, turtles respond with small upstream and downstream movements that keep them in a “box”—on the edge of the main flow where it’s always 0˚C with high DO, but no danger of being tumbled downriver. This can be fortuitous for the curious researchers following them. “Tracking wood turtles in winter is extra neat because you go out on fastmoving but ice-covered rivers,” enthuses Julia Riley. “Sometimes you can even see them through the ice.”