Amphibious Enclosures with Stream-side Enclosures

The stream-side enclosure is appropriate for amphibians that live on the margins of streams or ponds. These amphibians are generally good swimmers, and some spend considerable amounts of time in the water. Others stay on land or near the water’s edge, entering the water only to breed or travel to another bank. Stream-side dwellers include the stubfoot toads, Atelopus spp., the green frog, Rana clamitans, the bullfrog, Rana catesbeiana (also adapted to living in a pond habitat), the hairy frog, Trichobatracbus robustus, the tailed frog, Ascapbus truei, the American brook salamanders, Eurycea spp., the dusky salamanders, Desmognatbus spp., the spring salamanders, Gyrinophilus spp., and the Pacific giant salamander, Dicamptodon ensatus.

The basic stream-side enclosure (Plate 5.3, Figure 5.4) includes a stream and a land area covered with moss and/or leaf litter over a gravel substrate. The enclosure should be as long as possible to accommodate different aspects of the stream. The size of the stream should be tailored to the lifestyle of the species of amphibian being housed. It should have areas of faster and slower moving water, including riffles and relatively quiet eddies. If an amphibian has to struggle against a current for extended periods of time, it may become exhausted. The depth of the water should at no point exceed the shoulder height of the amphibian, unless the particular species is known to be a strong swimmer.

Figure 5.4. Lateral view of stream-side enclosure for amphibians. A. cross-section of board supporting the rim of the tank, tipping it toward the water outflow end. B. false floor assembly (see Figure 5.1 В—D). C. pea gravel layer approximately 5 cm (2”) thick. D. moist sheet moss. E. live, potted plant with the base of the pot resting on the fiberglass screen. F. riffle. G. waterfall running over rocks stacked to create moist crevice retreats. H. water outflow from the canister filter. I. hose fitting to spread the water flow. J. hole in tank wall just large enough to pass the canister filter tubing. K. lid (see Figure 5.1 E—H). L. mucky area. M. cork bark cave/feeding platform. N. eddy. O. water inflow to the canister filter. P. water line. Q. gravel siliconed to egg crate screening to form the streambed. R. drain assembly (see Figure 5.1 К—M). S. hardwood branch. T. streamway. U. rock perch. V. cork bridge over shallow water, providing a semi-aquatic retreat. W. leaf litter over moist sheet moss. (Sandy Barnett)

At the head of the stream there may be a waterfall formed from stacked rocks. Nooks and crannies in the rockwork may provide cool, wet retreats for the amphibians. A grooved piece of cork bark can be used as a stream base. The outflow from the canister filter can be directed to the high end of the cork, and water can spill down the cork into the pool at the far end. Alternatively, “egg crate” and plastic screening can be fastened together to form a channel for the stream bed. A combination of large river rock and pea gravel can be used to fill in the stream bed. The gravel can be bonded to the egg crate with silicon rubber to provide a secure framework for the stream, and loose gravel and rocks can be added to create the desired water movement. Large pieces of rock or wood can be oriented at an angle to the current to form eddies where water movement is minimal. A split section of PVC pipe can be used for the same purpose. The water in the stream-side enclosure needs to be well oxygenated at all times, which it will be if the current and stream contours are appropriate.

Ideally, the land area in the stream-side enclosure includes a moisture gradient ranging from saturated near the water’s edge and the waterfall, to fully drained but still slightly moist farthest from the stream. Small areas with dry, but not dusty leaf litter, dry rocks or fallen branches, and live plants will further diversify the moisture options available to the amphibian.

Living vegetation, rocks, branches, flower pots, and cork bark can be used to create terrestrial retreats, as well as refuges in shallow water. The latter refuges should allow the amphibian to rest in water no deeper than shoulder height, so that the animal can gulp air without treading water.

Some vegetation should be planted near and overhanging the streamway to provide cover and perches, as well as oviposition sites for some species of terrestrial and arboreal amphibians.