Small-mouthed salamander (Ambystoma texanum) COSEWIC assessment and status report: chapter 7

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Habitat

Known localities

General habitat requirements for A. texanum were provided in the 1991 status report (Bogart and Licht 1991) but limited information was provided with respect to the actual distribution of the Small-mouthed Salamander on Pelee Island. There are notable differences in the frequencies of A. texanum, A. laterale and the genomic hybrids from the five populations (Table 1). In this update, we include additional information on the sites that seems to be important for partitioning the salamanders on Pelee Island. The previous populations (Fig. 1) were re-visited and located using geographical coordinates (Appendix 1). Such data may eventually be combined with ongoing studies of the Blue Racer and the Eastern Fox Snake to document critical habitat for all these species.

At the Mosquito Point Woods locality, the habitat appeared virtually unchanged from the 1980s. There still exists a flooded woodlot with fallen logs and suitable habitat for the salamanders. The water level was low, compared with previous levels, which may pose a problem if the area dried before salamander larvae could transform. In one area where we observed breeding in 1984, the water depth was 50 cm and, at the same site in 2000, the water depth was only 20 cm. This area was normally dry by mid-August but transformation takes place through June and July. In April 2000, juvenile and adult salamanders were found under logs around the perimeter of the water. These salamanders were the only evidence that the population was still viable and that individuals were still being recruited into the population. Neither eggs nor larvae were observed. It was possible that breeding had not yet taken place or that breeding had been accomplished and the hatched larvae had dispersed through the thick layers of leaves that covered the bottom of the flooded woods.

The Quarry locality that has never yielded pure A. texanum individuals was also virtually unchanged from our previous investigations and many individuals of A. laterale and hybrids were found under rocks close to the water’s edge. This locality is an abandoned quarry with emergent vegetation surrounded by rocky outcropping at Sheridan Point. Again, the water level in the Quarry was noticeably lower but the Quarry pond is deep and maintains water all year so a slight reduction in the water level would not appear to be detrimental. Based on the numbers of salamanders observed in 2000 and the different sizes present, this population is dense and probably has remained unchanged.

The Stone Road locality is a flooded woodlot with a limestone base. Most of the specimens that were previously examined from this site were raised from eggs that were found early in the spring. Adults have never been found under debris close to the water and the breeding activity of adults has not been observed. The water varies in depth from 50 cm to about a meter. The submerged grasses and reeds are dense which renders observations of salamanders in the water difficult. In 2000, a large number of newly hatched larvae were observed among the vegetation in the water. There was no noticeable difference in this locality from our earlier studies.

The Pond is the most interesting of all the localities because it is the only locality that has been found to have both A. laterale and A. texanum as well as all genomic combinations of hybrids (Table 1). The water level has not changed from our previous investigations and remains constant all summer (Licht, personal observations). The pond is discrete, has a diameter of about 10 meters and is surrounded by small trees and bushes that overhang and enter the water. In the spring, salamanders are very common under the rocks that surround the pond.

The Girl Guide Pond and North End Woods sites were flooded woodland areas on the East side of Pelee Island adjacent to the perimeter road (East Shore Rd). The Girl Guide pond was located on the south side of the road that led from East Shore Rd. into the Township Campground that was used by the Girl Guides. The North End Woods site was a flooded area at the northeast end of the Island just south of Garno Rd. between East Shore Rd. and Clutton Rd. It is adjacent to the border of the Lighthouse Point Nature Reserve. Egg masses were collected from the Girl Guide Pond and larvae were netted at the North End Woods site during the spring of 1987. In March of 1989 there was no water at the same sites but adults were collected under wet logs. The four adult salamanders collected in 1989 from the Girl Guide site consisted of three female genomic hybrids (1 LT and 2 LTT) and one male Ambystoma texanum. Three adults were collected at the North End Woods site (1 LTT, 1 male and 1 female Ambystoma texanum). In 2000 the sites were dry and no salamanders were found.

Habitat trends

No breeding activity or specimens were observed in two of the five historical sites that were visited in the spring of 2000. The Girl Guide Pond and the North End Woods localities no longer exist and are dry areas. Previously, these two sites had the highest frequency of Ambystoma texanum (Table 1). No male A. texanum have ever been found at the Stone Road site. All larvae that transformed in the laboratory were determined to be female. That site was virtually unchanged in 2000 from our earlier investigations and still seems to have a very viable population as evidenced by the observation of numerous larvae. It would appear that the number of breeding sites and perhaps the range of A. texanum has been reduced.

Habitat protection

The most important population for A. texanum is in Mosquito Point Woods that is within the Provincial Park System’s Fish Point Nature Reserve. The Stone Road site is within a tract of land that is owned by the Federation of Ontario Naturalists and the Essex Region Conservation Authority. The Pond site is on privately owned land but the isolation of that population and the distance from both the road and from houses may provide some protection.