Friends of the Cawthra Bush
Greater Mississauga Area
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COLLEGE OF BIOLOGICAL SCIENCE
Department of Zoology
30 April 1998
Pete Lyons - Community Services Recreation and Parks
This has been a very strange spring. Most of the salamanders bred in that early warm spell and we have not had the necessary rains to have a good run. I think things are all finished for the salamanders.
I said that I would visit Cawthra Woods when the salamanders were breeding to gain a better appreciation for the habitat and to estimate the density of the population. Josh Feltham and I visited Cawthra Woods during the day and at night on April I st. We spent about three hours looking around the woodlot during the afternoon, attended a meeting with the Credit Valley Conservation group and returned to Cawthra Woods at night in a light rain.
Cawthra Woods has a good mix of deciduous trees and several wet areas. The relatively deep humus layer and rotting logs have a rich invertebrate fauna and should support large salamander populations. We encountered several Red backed salamanders (Plethodon cinders) in the southern area of the woodlot. We also found one Little Brown Snake (Starrier decay) under a piece of bark on the forest floor in the south-eastern part. Similar woodlots typically yield Red-backed salamanders (Plethodon cinereus), the Red Eft stage of the Spotted Newt (Notopthalmus viridescens), Red-bellied snakes (Storeria occipitomaculata) as well as the Little Brown snake, toads (Bufo americanus), and Wood frogs (Rana sylvatica). The fact that we did not find these other species should not be taken as absence but if these other species do occur there, they are not very common. The bricks and rubble around the ruins of an old budding and the pieces of machinery around an abandoned pump(?) are good places for snakes but we did not find any in those northern areas. We checked all the water bodies that might be expected to be used by Mole Salamanders (Ambystoma jeffersonianum, A. laterale, A. maculatum, and the hybrids associated with A. jeffersonianum and A. laterale) but no eggs were found in any pool or pond except the pond that is known to contain Mole Salamanders.
At night we were accompanied by Donald Barber and we all observed Jefferson complex salamanders in the pond and a few on land coming into the pond. We netted a few adults in the pond and most appeared to be the hybrid (A. laterale -(2) jeffersonianum (LJJ)) but one appeared to be an A. jeffersonianum female. There were a lot of salamanders in the pond laying eggs and we observed many egg masses attached to the leaves and small twigs in the pond. The pond did not seem to have either the Spotted salamander (A. maculatum) or Red-spotted Newts. It is unusual to have just the Jefferson complex salamanders breeding by themselves in such a pond. We did not see or hear any frogs nor did we see any frog egg masses. Again, this pond might have supported Wood frogs (Rana sylvatica), Leopard frogs (Rana pipiens), and Spring Peepers (Hyla crucifer).
Cawthra woods is an isolated woodlot and I don't think there is much possibility that the salamanders would immigrate or emigrate from the woodlot. The fact that the salamanders living there have flew competitors suggests that the population will probably remain stable if conditions do not change very much and if other species are not introduced that would provide some competition. The habitat might actually be enhanced to ensure the continued existence of the salamanders. The pond does have a deep layer of leaves and debris which might eventually reduce the water level or provide an anoxic environment. Some of this material could be raked out in the fall after the salamander larvae have transformed. The larvae transform in late July and August and the newly metamorphosed salamanders spend September close to the pond edge. October would be a good time to rake the pond. Sticks could be replaced or added to provide additional egg deposition sites. This would also be a good time to eliminate garbage from the water and to check for some permanent residents. If goldfish or turtles are introduced by some people with little knowledge of the effect of such introductions, this would have a disastrous effect on the salamanders. It is a common phenomenon in such a woodlot surrounded by urban development to have introductions by folks who get tired of their pets. I am of two minds about signage that might prevent such mishaps because other people who want to collect salamanders would be directed to such a site.
Other things that might be detrimental to the population would be to remove fallen trees and to cut out the larger hardwoods that provide tunnel systems around their roots. Decreasing the canopy would tend to make the area drier and this could reduce the food that the salamanders eat. The present mix of hardwoods and wet areas provides a good habitat. Compaction of the soil by numerous people walking through the woods would decrease the acceptable areas for the salamanders. The present path system appears very good as the paths are covered with mulch which reduces the compaction.
Monitoring the pond in the spring and estimating breeding success by observing egg masses should continue as this is the best way to see any trends that might take place over time. The salamanders live a long time and can adjust to the odd spring when there is reduced survival of the eggs but if such an event continues, other management practices should be considered. It must be remembered that the hybrids (LJJ) normally do suffer considerable mortality among the eggs so dead eggs are to be expected.
Josh Feltham, Donald Barber, and Heidi Shrouder collected some larvae from the pond on August 20th, 1997. These larvae were raised to transformation at Guelph and they all turned out to be the hybrid LJJ. My catalogue numbers for these specimens are 29268, 29270 - 75. Donald Barber gave me some frozen specimens that died. Four of the specimens were LJJ (29395-98) and one was a pure Ambystoma jeffersonianum (29394). This latter specimen confirms our suspicions that Ambystoma jeffersonianum does occur in Cawthra Woods and the male A. jeffersonianum is serving as the sperm donor for the hybrids that live there. These specimens will be deposited as vouchure specimens in the collection at the Royal Ontario Museum and represents an important new locality for this species (A. Jeffersonianum) and the hybrid associated with that species.
I think that is very fortunate that Cawthra Woods was brought to my attention and that I was able to sample some of the specimens. I appreciate the interest and the involvement of the Friends of the Cawthra Bush and I hope that they will continue to monitor the woodlot and raise questions that will preserve, this interesting and unique woodlot in Mississauga. I would appreciate being kept informed about the salamander population and offer my help if there is anything I can do to assist efforts to preserve this important site.
Sincerely - James P. Bogart
cc. Donald Barber, Friends of the Cawthra Bush - Josh Feltham, University of Guelph
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