Body condition analysis over time in Caiman latirostris

VIOTTO, E.; LEIVA, P.; CIOCAN, H; SIMONCINI, M.; PIÑA, C. I.

Santa Fe

Congreso; XXV Working Meeting Crocodiles Specialist Group - UICN.; 2018

Crocodile Specialist Group/IUCN

Climatic variables can affect the body condition (BC) of individuals because theydirectly influence the natural environment by modifying the availability of food. BC isan indicator of nutritional reserves; it can be calculated using indices that relate size andweight, which can be directly related to environmental parameters such as precipitationand temperature. We could then assume that, within a population, reproductive femaleswould possess the best BC, since they should provide part of their energy to producingtheir progeny (at a high energy cost). In addition, the BC of reproductive females, likethat of the rest of the population, would be affected by climatic variables. Using theBody Condition Index Scaled Mass Index (SMI) we compare the BC betweenreproductive (R) and nonreproductive (NR) individuals, and whether there weredifferences in BC between years, and if those differences could be explained by climaticvariables. We calculated the SMI for 335 individuals of C. latirostris captured from2001 to 2016, in the province of Santa Fe (Argentina). We classify the animals in NR(n=262): Class I, II, III (males and non-breeding females -proven by ultrasonography-)and class IV; and R (n=73): class III females with eggs (verified by ultrasonography)and females found next to their nests. We analyze the data using analysis of varianceand principal component analysis. We observed that the average population BC was4.35 (max:6.90; min:1.92; CV=16.08). The R's BC was greater than the rest of thepopulation (p<0.0001), 42.5% of the R individuals present values of SMI greater than 5,but only 10.5 % of the NR reach values greater than 5; for both R and NR individuals,the SMI varied between years (p<0.05) but was not related to the environmentalvariables tested. The bigger BC of reproductive females (R) could be due to the excessof energy stored to be used for reproduction. Variation on BC among years shows thatthe species has the ability to store more resources from the environment in some years.Environmental variables analyzed in this work were not related to BC, possibly otherenvironmental variables (water level, habitat complexity, number of days with low orhigh temperature), or intrinsic variables (habitat use, competition), could be affectingBC.