We conducted laboratory and field experiments to investigate the behavioral responses of Kemp's ridley Lepidochelys kempii and loggerhead turtles Caretta caretta to whole squid dyed different colors. Our ultimate goal was to identify bait modifications that could reduce the interaction of turtles with longline fishing gear. In captivity, both turtle species clearly preferred untreated squid over squid that had been dyed dark blue. Loggerhead turtles also preferred untreated squid over reddyed squid, whereas Kemp's ridley showed the opposite response. Field trials of blue-dyed bait were conducted on commercial fishing boats in the Gulf of Papagayo, Costa Rica, where the incidental capture of olive ridley turtles Lepidochelys olivacea is high (long-term average, approximately 7 turtles per 1000 hooks). We found no differences in rates of turtle interactions (8.4 and 8.1 individuals per 1000 hooks) when using untreated versus blue-dyed baits. Although effective in laboratory settings with captive turtles, dyeing bait does not appear to have potential as an effective mitigation measure to reduce sea turtle bycatch in longline fisheries. KEY WORDS: Sea turtle fisheries interactions · Bait color · Sea turtle bycatch mitigationResale or republication not permitted without written consent of the publisher

Effective management of protected sea turtle populations requires knowledge not only of mean values for demographic and life-history parameters, but also temporal and spatial trends, variability, and underlying causes. For endangered Kemp’s ridley sea turtles (Lepidochelys kempii), the need for baseline information of this type has been emphasized during attempts to understand causes underlying the recent truncation in the recovery trajectory for nesting females. To provide insight into variability in age and size at sexual maturation (ASM and SSM) and long-term growth patterns likely to influence population trends, we conducted skeletochronological analysis of humerus bones from 333 Kemp’s ridleys stranded throughout the Gulf of Mexico (GOM) from 1993 to 2010. Ranges of possible ASMs (6.8 to 21.8 yr) and SSMs (53.3 to 68.3 cm straightline carapace length (SCL)) estimated using the “rapprochement” skeletal growth mark associated with maturation were broad, supporting incorporation of a maturation schedule in Kemp’s ridley population models. Mean ASMs estimated from rapprochement and by fitting logistic, generalized additive mixed, and von Bertalanffy growth models to age and growth data ranged from 11 to 13 yr; confidence intervals for the logistic model predicted maturation of 95% of the population between 11.9 and 14.8 yr. Early juvenile somatic growth rates in the GOM were greater than those previously reported for the Atlantic, indicating potential for differences in maturation trajectories between regions. Finally, long-term, significant decreases in somatic growth response were found for both juveniles and adults, which could influence recruitment to the reproductive population and observed nesting population trends.

Field experiments have shown that parents in the colonially-nesting cliff swallow (Hirundo pyrrhonota) discriminate between their offspring and unrelated young whereas parents in the closely-related but noncolonial barn swallow (H. rustica) do not, and that discrimination is based on the chick begging call. In a laboratory experiment, we trained three cliff swallows, two barn swallows and a European starling (Sturnus vulgaris) to discriminate among chick begging calls of the two swallow species. All birds discriminated more easily among the calls of different cliff swallows than among the calls of different barn swallows, suggesting that cliff swallow calls are more individually distinctive, and may be adapted for a signature function. Moreover, cliff swallows discriminated among both cliff swallow and barn swallow calls faster than did the other birds, which is consistent with a perceptual adaptation for conspecific calls that incidentally facilitates the discrimination of similarly-structured heterospecific calls.

No abstract