Habitat disturbances differentially affect individual growth rates in a long‐lived turtle

Abstract

Disturbances often help structure ecological communities, and their impacts may have consequences on population dynamics and long-term species persistence. Should disturbances affect resources, a trade-off may result between reproduction and individual growth, which in turn could affect the timing of sexual maturity in animals dependent on reaching a requisite size for the onset of maturation. We used a 14-year mark-recapture dataset to determine the effects of catastrophic storms and the removal of nonindigenous vegetation on individual growth rates of a longlived turtle Terrapene carolina bauri. Adult male growth rates increased 19% after the disturbances, whereas female growth rates decreased by a similar percentage. Juvenile growth rates briefly increased, but as these animals became subadults, their growth rates slowed after disturbance, a change more pronounced in females than males. After the disturbances, the onset of male sexual maturity decreased by c. 1 years (from 10.8 to 9.5 years), female maturity was delayed by 2.5 years (from 8.5 to 11.0 years), and the subadult life stage was extended from 2 to 3.5 years. With resources and habitats similarly available to adults, we hypothesize that adult females diverted resources from growth to reproduction, whereas males allocated available resources to growth. Subadult growth rates decreased regardless of sex, implying that fewer or lower quality prey were available to smaller sized turtles in the years following disturbance. The results of this study suggest that habitat disturbances affected individual growth rates differently according to sex and life stage, which in turn affected the timing of maturation. In long-lived vertebrates, such perturbations on life-history traits such as growth rates likely affect population recovery, and may help to explain why turtle populations recover slowly following catastrophic disturbance, even when adult survivability is high.

Population structure and allometry of Podocnemis unifilis (Testudines, Podocnemididae) in a protected area upstream Belo Monte dam in Xingu River, Brazil

“…Monitoring such parameters is a core tool used in applied sciences of fisheries biology and wildlife management (Caughley and Sinclair 1994, Cadima 2003, Froese 2004. Population parameters of freshwater turtle species have been comparatively analyzed at temporal and spatial scales to study the effects of particular environmental conditions, habitat alteration and human pressure on the environment (Marchand and Litviatis 2004, Steen and Gibbs 2004, Dodd and Dreslik 2007 another tool used in applied sciences to monitor and evaluate the status of wild populations. The most common is the length-weight relationship (LWR), used to convert lengths into biomass, to determine fish stock status, to compare fish growth amongst areas, and also as a complement to species-specific reproduction and feeding studies (Froese 2006).…”

Demographic differences among populations of Northern Map Turtles (Graptemys geographica) in intact and fragmented sites

“…A possible explanation for the high proportion of females and juveniles in our fragmented populations arises from a study by Dodd and Dreslik (2008), who examined a population of Florida Box Turtles (Terrapene carolina bauri Taylor, 1895) following habitat changes caused by hurricanes and exotic vegetation removal. Adult female Box Turtles decreased their growth rates following a catastrophic event (Dodd and Dreslik 2008).…”

“…A possible explanation for the high proportion of females and juveniles in our fragmented populations arises from a study by Dodd and Dreslik (2008), who examined a population of Florida Box Turtles (Terrapene carolina bauri Taylor, 1895) following habitat changes caused by hurricanes and exotic vegetation removal. Adult female Box Turtles decreased their growth rates following a catastrophic event (Dodd and Dreslik 2008). The authors hypothesized that adult females were preferentially funnelling energy resources into reproduction instead of growth postdisturbance (Dodd and Dreslik 2008), based on an increase in juvenile recruitment found in a previous study (Dodd et al 2006).…”

Effects of an exceptional drought on daily activity patterns, reproductive behaviour, and reproductive success of reintroduced Arabian oryx (Oryx leucoryx)

“…Much less emphasis has been placed on anticipated changes in weather variability. Of particular interest are extreme events such as windstorms (e.g., Dodd and Dreslik, 2008;Spiller and Schoener, 2007), floods (e.g., Plath et al, in press), droughts (e.g., Holmgren et al, 2006; this study), etc. In the last decade, the number of catastrophic weather events was three times as great, and the cost to the world economies eight times higher than in the decade of the 1960s (MacDonald, 1999).…”