Factors limiting early life stage survival and growth during endangered Wyoming toad reintroductions

Abstract

Understanding the limiting factors of recovery is essential for guiding sound management of endangered species. The Wyoming toad (Anaxyrus baxteri) is a critically endangered amphibian whose cause of decline and inability to reestablish breeding populations despite early life stage reintroductions remains unknown; habitat degradation and the pathogen Batrachochytrium dendrobatidis (Bd) are 2 potential contributing factors. In 2013, we experimentally tested the effects of habitat factors under foodsupplemented and predator-protected conditions (i.e., mesh field enclosures) on time to metamorphosis, the proportion of tadpoles that metamorphosed, tadpole and toadlet size, the proportion of toadlets remaining in enclosures at release (approx. 1 month post-metamorphosis), and Bd prevalence in early life stages of Wyoming toads at Mortenson Lake National Wildlife Refuge. In 2014, we tested the effects of small-scale application of vegetation height management on toadlet size, the proportion of toadlets that remained, and Bd prevalence until 1 month post-metamorphosis. In 2013, median time to metamorphosis (25.5 days) was shorter in warmer water temperatures and proportion of tadpoles that metamorphosed was 0.70. In 2013, toadlet size was positively related to forb cover up to 35% and although overall treatment effect was not significant, mid-vegetation height treatments (10-30 cm) had fewer small toadlets at release than short (0-10 cm) and tall (>30 cm) vegetation heights. In 2014, vegetation height treatment (11.49-31.6 cm) had marginal support for estimating larger size at release. Batrachochytrium dendrobatidis was not detected in water samples or on post-metamorphic toadlets. Our results suggest that in mesh field enclosures, time to metamorphosis is shorter in warm water. In addition, vegetation heights of 10-30 cm and up to 35% forb cover within terrestrial mesh enclosures could increase Wyoming toad post-metamorphic size, which could increase overwinter survival rates. Using mesh field enclosures for soft-release may improve the effectiveness of early life stage reintroduction efforts, but predator attraction and density-dependent growth need to be considered. Habitat management can also influence growth and survival of early life stages of amphibians and may benefit reintroduction efforts for other species. Ó 2015 The Wildlife Society.

Draft for Open Consultation. The Amphibian Conservation Action Plan (ACAP): A status review and roadmap for global amphibian conservation.

“…Amphibians also act as pest control in agricultural habitats as they are generalist feeders and ingest all types of invertebrates, including pests such as locusts (Attademo, Peltzer & Lajmanovich, 2005), thus naturally improving crop yields, especially rice (Teng et al, 2016) and soybean (Attademo, Peltzer & Lajmanovich, 2005).…”

“…There are also documented instances of lost support. For example, the United States Fish and Wildlife Service (USFWS) managed the Amphibians in Decline Fund, which supported conservation efforts in 25 countries from [2010][2011][2012][2013][2014][2015][2016]. Unfortunately, the programme ended once funding dried up (Scott, 2021).…”

“…Updating estimates from Barnosky et al (2011) to reflect current IUCN Red List assessments of recognised extinctions and current species richness (AmphibiaWeb, 2020), we estimate an amphibian extinction rate of 9 extinctions per 1000 species per 1000 years (or million species-years) over the past 500 years. Estimating extinction at the same time scale, but limiting it to those species for which climate change has been implicated as a threat (currently 6 species categorised as Extinct or Extinct in the Wild), results in 1.5 extinctions per million species-years.…”

“…Data are beginning to suggest that chemical types and classes do have generalizable consequences. To evaluate chemical classes, Shuman-Goodier & Propper (2016) found effect sizes for swim speed and activity in fish and amphibians were similar for contaminants within the same chemical class. Using a meta-analysis, Egea-Serrano et al (2012) determined that types of contaminants had different effect sizes across amphibian responses, suggesting that some contaminant types were more likely to have negative effects.…”

Transcriptome Annotation Reveals Minimal Immunogenetic Diversity Among Wyoming Toads, Anaxyrus Baxteri

“…This species maintained a stable population up until the 1970s when it experienced a rapid decline, was declared endangered in 1984, and thought to be extinct by 1985 (Vincent et al 2015). While the cause for the rapid decline of the species is not de nitively known, dramatic changes in land use practices and the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd) likely played a role (Dickerson et al 2003;Dreitz 2006; Burton et al 2009;Hornyak 2012;Polasik et al 2016). Two years following the presumed extinction of the species, a small population was discovered at Mortenson Lake in Albany County.…”