Manipulating waterbody hydroperiod affects movement behaviour and occupancy dynamics in an amphibian

Abstract

Species that occur in ephemeral habitats such as temporary waterbodies have evolved specific strategies that allow them to respond to spatial and temporal variations in water availability and quality. Their life‐history strategies, involving complex life cycles, have evolved to allow individuals to escape deteriorating environmental conditions when a waterbody dries up. These adaptations have led to the emergence of complex movement behaviour, which might then be expected to affect the spatiotemporal dynamics of reproduction. To date, few empirical studies have investigated how the risks of waterbody drying out affects movement behaviour at the individual level and how movement decisions then shape waterbody occupancy dynamics. In this study, we examined this issue in an endangered amphibian, the yellow‐bellied toad (Bombina variegata). For this purpose, we experimentally manipulated waterbody hydroperiod and collected capture–recapture and presence–absence data in 334 waterbodies located in 15 B. variegata populations in the region of Geneva (Switzerland) during a 5‐year period (2012–2016). The results of our analyses reveal that the waterbody hydroperiod affects this species' movement behaviour. Adults were less likely to leave waterbodies with a long hydroperiod both intra‐ and inter‐annually. In addition, breeding occupancy strongly depended on a waterbody's hydroperiod. In particular, interannual changes in breeding occurrence were less frequent in waterbodies with a long hydroperiod. Our findings show that the hydroperiod strongly affects ecological processes at different levels, from individuals' movement decisions to waterbody occupancy dynamics. The results demonstrate that adults adjust their movement decisions according to the risk of breeding failure driven by the hydroperiod, which then affects the waterbody occupancy dynamics.

Habitat‐driven life history variation in an amphibian metapopulation

“…This is also congruent with our knowledge of the natural history of B. variegata. Previous studies have shown that breeding probability increases with precipitation over the breeding season (Cayuela et al 2014(Cayuela et al , 2017 and that adults focus their breeding effort on ponds with limited water level variation (Tournier et al 2017). In our study system, individuals reproducing in variable sites had a higher propensity to skip breeding, likely because water levels in ponds are often too low for successful tadpole development.…”

Quantifying data quality in a citizen science monitoring program: False negatives, false positives and occupancy trends

“…Consequently, we also have F I G U R E 5 Number of occupied sites for a rare species, the common Midwife toad Alytes obstetricans over 10 core areas (panels). The usual approach "pond = population" may be wrong because within-season movements between sites appear to be common in amphibians (Kopecky, Vojar, & Denoel, 2010;Petranka et al, 2004;Schmidt, 2005;Tournier, Besnard, Tournier, & Cayuela, 2017). The line for raw data represents the number of sites at which observations were made in the dataset (i.e., assuming no false-positives and perfect detection) less confidence that site 3 is truly unoccupied, as the probability of not detecting it even if it is there also increases to 12.5% (i.e., (1 − 0.50) 3 ).…”

“…The best solution to the issue of transient individuals (ecological false positives) is the careful definition of sampling units when designing a study (Altwegg & Nichols, 2019;Petranka, Smith, & Scott, 2004). The usual approach "pond = population" may be wrong because within-season movements between sites appear to be common in amphibians (Kopecky, Vojar, & Denoel, 2010;Petranka et al, 2004;Schmidt, 2005;Tournier, Besnard, Tournier, & Cayuela, 2017). In situations where ecological false-positives cannot be prevented during the planning stage of monitoring, models such as ours-which can account for both forms of false-positive observations-are recommended in order to improve inference of occupancy dynamics and trends (Altwegg & Nichols, 2019;Sutherland et al, 2013).…”

Demographic response to patch destruction in a spatially structured amphibian population

“…In B. variegata, females avoid spawning in waterbodies where conspecific tadpoles occur to limit the risk of intraspecific competition at larval stage (Cayuela, Lengagne, Joly, & Léna, 2017;Cayuela, Lengagne, et al, 2016). In contrast, studies showed that waterbody drying out was the most important factor of larval mortality in this species and that adult adjust their breeding decision according to desiccation risks (Barandun et al, 1997;Tournier, Besnard, Tournier, & Cayuela, 2017). Therefore, we have chosen to consider the effect of environmental stochasticity on fecundity rather than that of density dependence.…”