Spatio-temporal patterns in beaver pond complexes as habitat for Eastern Spotted Newts (Notophthalmus viridescens) in a hemlock-northern-hardwood zone in Western New York State
Amphibians are among the most threatened of animal groups, so understanding the nature and dynamics of their habitats is essential to their conservation. The Eastern Spotted Newt (Notophthalmus viridescens) strongly prefers shallow quiescent soft-bottomed habitat, generally in small streams and pools. An increasingly abundant and widespread source of such habitat in the Northeast has been beaver ponds. Within the 27K ha Allegany State Park, NY (our study site), beaver populations have recovered to where there are now hundreds of active sites among the 1st – 4th-order streams within the park. The main objective of this study is to determine the influence of size, age, and stability of beaver ponds on their use as spotted newt habitat. Georeferenced aerial and satellite imagery of four multi-pond beaver complexes, coupled with ground-truthing, are used to assess the spatio-temporal framework of ponds, including patterns of senescence and reestablishment of dams. Flow regime, sedimentary environment, and submerged/emergent vegetation are being described for various micro-habitat types at each pond. Simple but non-invasive visual surveys of newts in shallow water within 1 m of shoreline are being used to estimate their use of habitat.
Spatio-temporal dynamics of pond complexes are highly variable, with some existing for decades and others only a few years, and some perennially stable with others senescing and rebuilt as frequently as each season. Spotted newts are clearly most abundant in shallow areas of soft sediments with plant debris, and rare on gravel bottoms. They are also most abundant in blind-ended coves and back-flooded feeder streams, but generally not along the backside of actual dams. Newts are entirely absent from fast-current gravel-bottom channels that form when dams are breached. Newt populations are very patchy even in apparently preferred habitat, often absent but occasionally up to 10 per m2. Results thus far suggest newt densities are highest within the most stable of the studied pond complexes. Curiously, newts are scarce in the flooded upstream margins of three artificial impoundments (which are of course temporally stable), but these environments are modified by human activities, so the implications of this finding are are not known. It is clear at the landscape scale of the entire park that beaver pond complexes are by far the dominant spotted newt habitat.