Strong Climate Associations but No Temporal Trends in Nesting Phenology of Blanding's Turtles (Emydoidea blandingii)

Abstract

Climate change has caused substantial shifts in the phenology for many species across a broad array of life-history events. Ectotherms are no exception; recent studies have discovered strong climate associations with nesting phenology for many turtle species. We studied phenology for the International Union for Conservation of Nature (IUCN)-endangered Blanding's Turtle (Emydoidea blandingii) across 16 yr in Wisconsin, USA to assess the potential for climate-associated shifts in this species. We hypothesized that, as with other freshwater turtles, Blanding's Turtle nesting phenology should be a function of climate. Furthermore, phenological shifts should be relatively consistent among nest sites within our study area given the scale of climate effects. Although nesting phenology did not advance significantly through time, nesting phenology was linked to March temperatures and was earlier in warmer years. Effects of March temperatures on nesting phenology were similar among nesting sites. Although no temporal trends in nesting phenology were evident, the strength and spatial uniformity of climate associations with nesting behavior documented by our study indicate that phenological shifts are likely, highlighting an additional form of climate vulnerability not previously recognized for this species.