Winter survival of Caiman latirostris hatchlings: preliminary results

VIOTTO, E.; SIMONCINI, M. S.; NAVARRO, J.; PIÑA, C.I.

Chetumal

Congreso; XXVI Working Meeting Crocodiles Specialist Group - UICN; 2022

Crocodiles Specialist Group - UICN

To know winter survival and movement of Caiman latirostris hatchlings(CI<25cm SVL) we released 18 animals (15.5±1.1cm SVL) with radiotransmitters in Santa fe province, Argentina. We recorded the location of each transmitter, assigning each encounterto one of the following categories: Alive, Dead, Unseen, or Transmitter withoutthe animal (TW). In a 106-day interval, we made six field trips, finding 55.5%of the individuals dead and 44.5% TW. We used the Kaplan-Meier test to evaluatesurvival under four possible scenarios, depending on whether each TW was takenas if the individual had been Alive or Dead: E1, all alive; E2: seven alive(all TW except the individual whose transmitter we found outside the lagoon);E3: two alive (transmitters without marked scratches on their carcass); and E4:all dead. Although we could not find any individual alive, the estimatedsurvival probability for E1 was 38±13%, for E2 35±12%, for E3 11±7%, and for E40%. Caiman movements were heterogeneous: while five individuals remained close(between 0-30 m) to the release site, the rest firstly moved between 80-247 mand afterwards their displacements were circumscribed within a small area.Although we can only ascertain for those killed by thermal stress (38%), it ismost plausible that, including predation and taking E3 as reference, survivalis around 11%. However, considering that we have only evaluated a portion ofthe first year, and the animals were kept in captivity for 2.5 months, the first-yearmortality may be higher. Our findings regarding the mobility of CI show thenecessity to thoroughly evaluate in advance the suitability of sites where hatchlingsare planned to be released, to maximize their survival in the long term, as theydo not move too much.