WINNIPEG FREE PRESS (Manitoba) 29 August 04 Squeezing out the skink - Manitoba's only lizard in danger from encroaching aspen (Tina Portman)
Jacey Scott and her assistant, Judy Hodge, are looking intently at a piece of three-quarter-inch spruce plywood. It's one of almost 250 30-by-60-centimetre boards that Scott has scattered among the patches of mixed-grass prairie, shrubby grassland and aspen forest in Spruce Woods Provincial Park.
Hodge kneels by the board, Scott crouches on the other side. "Ready?" Scott asks Hodge. She lifts the board. Nothing moves. Quickly, she pats the grass, just in case. Nothing.
Disappointed but not surprised, they replace the board and Scott pushes one thermometer under it, one above it and one beside it into the soil. It's mid-summer. Pincushion cactus and three-flowered avens bloom among the blue grama and sand bluestem grasses. The temperature above the board is 42degreesC. Beneath the board, it's 31, and in the soil, it is 21. This board has been vacant all month, even though it's in a south-facing, open mixed-grass prairie habitat -- a good spot for Manitoba's only lizard, the northern prairie skink.
Skinks are cold-blooded. They burrow under the boards, where they are protected from hawks, and down into the vegetation and soil until they find a comfortable body temperature, ideally around 30degreesC. Skinks need light, sandy soils, which are loose enough to allow the tiny lizards (they are only 13 to 20 centimetres long, most of which is tail) to burrow below the frost line for winter hibernation.
Canada's population of northern prairie skinks is found only in the 1,800-square-kilometre Carberry Sandhills in southwestern Manitoba. This is an isolated population of skinks. The range of the rest of the northern prairie skink population starts 500 kilometres south, in the southeast corner of North Dakota.
Scott, a master's graduate student in teh faculty of environment at the University of Manitoba, has been studying prairie skinks at Spruce Woods for two years. She is documenting which habitat types they use and which they don't. It's slow and methodical work. In 2002, in three months of almost daily excursions into skink habitat and 900 board checks, she found only 10 skinks. In 2003, she found 75.
Last year, Scott glued one-centimetre radio transmitters to the backs of six skinks (the transmitters fall off in a few days). She tracked the signals and found that when the skinks weren't under the research boards, they were often deep in the middle of clumps of little bluestem grass. Little bluestem grows in a dense bunch that sits on the sandy soil like a spike-haired baseball. Even when Scott knew a skink was hiding underneath, she couldn't poke her fingers far enough into the grass knob to find it.
Scott and Hodge inspect more study boards. Underneath one are half a dozen black crickets, a preferred skink food.
"There's no skink here," says Scott.
Under another board, they find a moulted skink skin. It looks like a snakeskin, papery and scaly, but with leg holes.
At the next board, Scott and Hodge move quickly. Hodge whips her hand around a green snake. The green snake is a neat find. It's 30 centimetres long, dirty looking and its eyes are milky, signs that its outer skin is drying and it will soon moult. Kneeling beside Hodge, Scott holds a prize -- a skink.
The skink has a brown-olive back, a pale belly and black stripes that extend from each eye back along each side of its body. In breeding season, males have bright orange throats, so this earth-coloured skink is a female. The skink has been caught before under this same board. She has one green dot on her abdomen, a harmless elastomer that Scott injects just below the skin to identify individuals. Scott wasn't surprised to find her under this board again.
Skinks have extremely small home ranges. A skink may live its entire life in an area half the size of a tennis court or smaller. They prefer to stay in one place if they can. A pair of skinks once lived for six years under a fallen 25-by-30 centimetre metal Manitoba Natural Resources sign.
When home is so small, it has to be excellent habitat. Scott has found that although skinks prefer south- and west-facing slopes in mixed-grass prairie, they will also live on north-facing slopes or, rarely, shrubby areas. They seem to like areas with clumps of little bluestem and spreading shrubs, like juniper -- good for hiding in the shade on hot summer days. Skinks do not live in white spruce or aspen forest.
This is a problem for skinks in Spruce Woods, which holds almost 15 per cent of the province's skink habitat. Eighty years ago, the land that is now Spruce Woods was mixed-grass prairie ranchlands, a sea of potential skink habitat. Ranchers would climb one of the scattered white spruce trees and scan kilometres of grassland to find a lost cow. With the absence of the two grassland rejuvenators, bison grazing and fire, most of the grasslands in the park have been swallowed by trembling aspen. The prairie has become a forest.
West of Spruce Woods, the CFB Shilo military training range is completely different. Grass fires started by shells during training exercises have renewed and preserved the native grasslands. On an aerial photograph, there is a clear demarcation between the forested Spruce Woods and the open grasslands on the military range.
"You can tell right away, looking at the vegetation, that skinks are going to have trouble in Spruce Woods Provincial Park unless something is done," says Scott. "If the aspen comes in and squeezes them out, skink populations will go down."
Manitoba Conservation's park managers have started a burning program to keep encroaching aspen out of 16 of the park's grassland remnants. They've released beetles into over 200 grassland sites to control leafy spurge, an eastern European weed that smothers prairie and evicts native species, including skinks. Manitoba Conservation, through the wildlife and ecosystem protection branch, also funds part of Scott's research.
Still, skink habitat is disappearing under aspen and leafy spurge. Habitat loss is especially threatening for Manitoba skinks because they are found in such a small, isolated area. If things get bad at home, Manitoba skinks can't make the 500-kilometre trek to the closest skink habitat in southeast North Dakota. Because of their isolation and declining habitat, this May the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) downgraded the northern prairie skink from its 1989 assessment as a species of "special concern" to its current designation of "endangered." COSEWIC scientists believe the skink is likely to disappear from Canada if habitat loss continues.
Errol Bredin, co-author of the COSEWIC skink status report, has studied reptiles in the Carberry Sandhills for 40 years. "Skinks aren't on the verge of completely disappearing," says Bredin, "but the fear is that they are limited to a relatively small area -- the Carberry Sandhills. The Sandhills cover a sizable area, but in terms of species and future species health, it's a relatively small area. As portions of that disappear, there's a great fear that 15 to 20 years from now there will be little left of the necessary habitat to support a species such as the skink. And that -- that's a great fear."
Scott and Hodge have finished their fieldwork for the day. As they walk back to Scott's brown Dodge Shadow, Hodge is telling skink tales. Earlier in the summer, Hodge cupped her hand over a skink. It wiggled. It writhed. She said to Scott, "Wow, is this one ever feisty!" When she peeped under her hand, all she had was a tail.
This is a skink's main defence mechanism. While the skink runs away, its tail keeps twitching for up to 15 minutes. The skink grows another tail.
On another occasion, a skink played dead. In the time it took Hodge and Scott to say, "Oh no! We've killed it!," the skink was gone.
"That's the best part about the job," says Scott -- "finding skinks." Scott likes the five-centimetre, blue-tailed juveniles that hatch from soft-shelled eggs in August. "They're so small, it's amazing that they last the winter."
Although Scott and Hodge spend a lot of time looking under empty boards, Scott is optimistic about the future of her study species in the park, provided the aspen can be kept at bay.
"There's a good population of skinks in Spruce Woods Provincial Park," says Scott. "It's an ideal place for skink conservation."