Testing whether conservation action works: Does the creation of stepping-stone ponds increase dispersal?
Date:
Awarded Best Student Talk
Summary
Habitat loss and fragmentation are among the major threats to amphibians, leading to the isolation of sub-populations and consequently increased mortality rates. The creation of habitat connectivity features is commonly cited as a target for conservation work, with the aim of increasing dispersal and gene flow between isolated populations. Howeverthe degree to which such projects are successful is rarely tested. We assessedthe effectiveness of a pond-building project in Switzerland by examining movement patterns of the Yellow-Bellied Toad (Bombina variegata)over the course of one such program.
In 2011 eightisolated populations of B.variegatawere identified in the Schwyz regionand a mark-recapture study was initiated. Since 2011 tennew pond complexes have been dug in the study area in order to increaseconnectivity and thusmigration between the original ponds. Between 2011-2014 we identified over 2500 individuals from nearly 5500 captures. Individuals were captured at 50% of the newly constructed ponds, however of the 79 individuals caught atthese ponds, only 4 had been previously identifiedat other locations in the study area.Monthly survival rates were variable between sites but generally high (>95%).
These results suggest that although B.variegataare considered a pioneerspecies, and indeed rapidly colonised several of the new ponds in our study area,the rates at which individuals successfully reach suitable pond habitat is relatively low. Furthermore,the vast majority of recaptured individuals remained at their original site of capture, suggesting that once individuals reach suitable breeding habitat they exhibit high site fidelity.
In conclusion, it appears that unless habitat “stepping stones” are located very close to existing populations, they are unlikely to become colonised by B.variegataand so are unlikely to succeed in reconnecting remnant populations.Future work in this study will involve characterising population structure and the source of colonising individuals using genetic markers, and tracking the spread of the fungusBatrachochytrium dendrobatidis, discovered in the study area for the first time in 2014, in relation to amphibian movements.