Adult Recruitment in Chorus Frogs: Effects of Size and Date at Metamorphosis

TLDR

The study aimed to assess how body size and metamorphosis timing affect chorus frog survivorship to maturity. Researchers classified metamorphosing frogs into large‑early, small‑early, large‑late, and small‑late groups and monitored their return to breeding over two years. Long larval periods and small size delayed maturity, whereas large size and early metamorphosis increased survivorship by reaching reproductive size within a year; after two years all size/date categories were equally represented, indicating post‑metamorphosis survival is independent of size or date unless breeding occurs in the first year.

Abstract

A cohort of tadpoles of the chorus frog, Pseudacris triseriata, on Isle Royale, Michigan, was marked to determine the effect of body size and date at metamorphosis on survivorship to maturity. The cohort was classified at metamorphosis into four categories based on size and date of metamorphosis: large—early, small—early, large—late, and small—late. The number of frogs in each category that returned to breed on the study area was monitored for the following 2 yr. Long larval period and small body size at metamorphosis influenced recruitment to the breeding population by delaying maturity. Frogs that metamorphosed at large size maintained their size advantage at maturity. Large body size and early date at metamorphosis increased survivorship to maturity by enhancing the chance that reproductive size was attained within 1 yr of metamorphosis. Frogs that were recaptured in the 2nd yr after metamorphosis, when all frogs had attained mature size, were from all four categories in the same proportions marked at metamorphosis, indicating that unless breeding during the 1st yr, led to higher mortality of large individuals, survival rate after metamorphosis was not related to size or date at metamorphosis.