Conditions controlling the timing of the autumn migration to hibernation sites in a Japanese headwater frog, Rana sakuraii

Abstract

Studies on amphibian autumn migrations to hibernation sites are few, and those investigating the conditions controlling the timing of migrations are even fewer. I investigated an explosive-breeding frog, Rana sakuraii, in Japanese mountain headwaters in 6 different years, focusing on the start and end of autumn migrations. Autumn migrations began in late October. Initially, frogs moved into the streams from terrestrial sites around the stream sources, and thereafter moved downstream entirely underwater. Start days were always the first rainy days after the minimum air temperature had dropped to about 6°C or lower (minor start days) or about 4°C or lower (major start days) regardless of the air temperature on the start days. In early or mid-December, in-stream migratory movements ended when the maximum water temperature dropped below the 5°C threshold (the same threshold temperature initiating the winter breeding migration). I hypothesize that, in many temperate-zone amphibians, the timing of autumn migration to hibernation sites is basically dependent on three common conditions: (1) the experience of a prerequisite minimum air temperature (PMAT) before the start day; (2) the decrease in day length to a threshold value; (3) the first rainy (or high humidity) day after (1). Further, I hypothesize that the threshold ambient temperature inducing the end of the autumn migration is almost the same as that inducing emergence from hibernation, that is, the start of the winter breeding migration for explosive breeders, and that this is the daily maximum, and not the daily minimum.

Biological Diversity in Headwater Streams

“…Some species of freshwater shrimp move seasonally to headwaters to breed [15]. Some frogs move in autumn into headwater streams, then swim downstream to find hibernation sites and move back upstream the following summer to breed [51]. Desmognathus salamanders showed a propensity for upstream movements towards headwaters [16].…”

The Behavior of Amphibians Shapes Their Symbiotic Microbiomes

“…When the temperature rises, amphibians such as Ambystoma opacum migrate to ponds or wetlands to breed, to ensure the survival of their offspring ( 3 – 5 ). When the temperature decreases, amphibians migrate to hibernation sites to maintain their body temperature during the cold winter ( 6 ).…”

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“…Natterjack Toads (Epidalia calamita) in Britain have been observed to shift refuge sites in response to tidal inundation (Denton and Beebee 1993). More probably, however, the combination of environment conditions, such as colder temperatures, increased rainfall, and decreased day length that appears to evoke pre-hibernation movements in other anurans (Koskela and Pasanen 1974;Miwa 2017) also contributed to the behavioural changes seen in these toads. Fowler's Toads at Long Point are not active in the spring at temperatures below 14°C (Green 1989(Green , 2005; thus, the nighttime low temperatures following the storm approached the lower limits of the toad's normal activity range.…”

“…Snapping Turtle was listed Vulnerable under the Nova Scotia Endangered Species Act in 2013, but to date, the presence of a naturally occurring population has not been recognized on Cape Breton Island (COSEWIC 2008;Environment and Climate Change Canada 2016). This paper discusses the status of Snapping Turtle on Cape Breton Island, summarizes known distribution based on personal observations as well as records from NSDNR and NSM (n = 75;1953-2017, and presents data on time of nesting, location of nests, clutch size, time of emergence of hatchlings, survivorship to emergence, and size of hatchlings for nesting areas located at Huntington, Cape Breton County, Nova Scotia.…”

“…Compared with their spring movements to aquatic breeding sites, the autumnal movements of temperate zone, pond-breeding amphibians to overwintering sites are not well understood (Miwa 2017). However, there is evidence that anurans may alter their habitat preferences late in their active season and begin to seek particular sites for hibernation that they would otherwise tend not to use (Koskela and Pasanen 1974;Bull 2006;Lee and Park 2009;Yu and Guo 2010;Ludwig et al 2013).…”