Performance of different automatic photographic identification software for larvae and adults of the European fire salamander.

For many species, population sizes are unknown despite their importance for conservation. For population size estimation, capture-mark-recapture (CMR) studies are often used, which include the necessity to identify each individual, mostly through individual markings or genetic characters. Invasive marking techniques, however, can negatively affect the individual fitness. Alternatives are low-impact techniques such as the use of photos for individual identification, for species with stable distinctive phenotypic traits. For the individual identification of photos, a variety of different software, with different requirements, is available. The European fire salamander (Salamandra salamandra) is a species in which individuals, both at the larval stage and as adults, have individual specific patterns that allow for individual identification. In this study, we compared the performance of five different software for the use of photographic identification for the European fire salamander: Amphibian & Reptile Wildbook (ARW), AmphIdent, I3S pattern+, ManderMatcher and Wild-ID. While adults can be identified by all five software, European fire salamander larvae can currently only be identified by two of the five (ARW and Wild-ID). We used one dataset of European fire salamander larval pictures taken in the laboratory and tested this dataset in two of the five software (ARW and Wild-ID). We used another dataset of European fire salamander adult pictures taken in the field and tested this using all five software. We compared the requirements of all software on the pictures used and calculated the False Rejection Rate (FRR) and the Recognition Rate (RR). For the larval dataset (421 pictures) we found that the ARW and Wild-ID performed equally well for individual identification (99.6% and 100% Recognition Rate, respectively). For the adult dataset (377 pictures), we found the best False Rejection Rate in ManderMatcher and the highest Recognition Rate in the ARW. Additionally, the ARW is the only program that requires no image pre-processing. In times of amphibian declines, non-invasive photo identification software allowing capture-mark-recapture studies help to gain knowledge on population sizes, distribution, movement and demography of a population and can thus help to support species conservation.

Stress response of fire salamander larvae differs between habitat types.

The larvae of the European fire salamander (Salamandra salamandra) can inhabit two different habitats: streams and ponds. Streams are characterized by lower predation risks and higher food availability. Thus, ponds are considered a less suitable habitat. To investigate the differential impacts of these two habitats on larval physiology, we measured the stress response of larvae. After successfully validating the measure of water-borne corticosterone release rates in fire salamander larvae, we measured the baseline and stress-induced corticosterone of 64 larvae from ponds and streams in the field. We found that larvae in ponds have a higher baseline and stress-induced corticosterone levels. Additionally, we performed a reciprocal transplant experiment (RTE) and tested whether larvae can adapt their stress responses to changing habitats. After two weeks, we did not find an increase in corticosterone levels when comparing stress-induced corticosterone values with baseline corticosterone values in larvae transferred into ponds, irrespective of their habitat of origin. However, larvae transferred into streams still exhibited an increase in the stress-induced corticosterone response in comparison with the baseline values. These results show that non-invasive hormone measurements can provide information on the habitat quality and potential adaptation and thus emphasize the potential for its use in conservation efforts.

Locality, time and heterozygosity affect chytrid infection in yellow-bellied toads.

The chytrid fungus Batrachochytrium dendrobatidis (Bd) infects numerous amphibian species worldwide and is suggested to drive population declines and extinction events. We report a study of Bd infection at the northernmost distribution of the European yellow-bellied toad Bombina variegata. A total of 577 individuals from ponds in 16 study sites were sampled for DNA and Bd throughout the breeding season. Microsatellite genotyping revealed 3 genetic clusters for the host B. variegata with an overall low genetic diversity. One of the clusters displayed a low microsatellite heterozygosity, a high inbreeding coefficient as well as high Bd infection prevalence and intensities. Multi-model estimates identified site, time of sampling, and heterozygosity to be important predictors of an individual's Bd infection status, and identified a strong effect of site on individual Bd infection intensity. The study site effects are suggestive of localized infection peaks, and the increase of individual Bd infection probabilities towards the end of the sampling period suggests cumulative infection during the breeding season. This study highlights the need for regular monitoring of Bd infection variables at multiple localities and times to gain insights into Bd dynamics. Due to the detected relationship between individual Bd infection status and heterozygosity, conservation measures should focus on the maintenance of high genetic diversity and connectivity within and among amphibian populations.