Body Condition of Reproductive and Non-Reproductive Broad-Snouted Caiman Females

Abstract

In this work, we calculated the body condition indices, K-Fulton and scaled mass index (SMI), of reproductive and non-reproductive Caiman latirostris adult females as an indication of stored energy. We considered 87 adult females captured from 2001 to 2018, both reproductive and non-reproductive. The body condition was calculated considering two scenarios: (a) only the weight of the female, and (b) the sum of the weight of the female and the average dry weight of her nest. We tested the difference in body condition between reproductive and non-reproductive females. We also evaluated the minimal body condition required to guarantee that females above it are reproductive by drawing a line that separated the body condition of strictly reproductive individuals from those that may or may not be reproductive. Reproductive females had better body condition than non-reproductive ones. Our SMI.S line separated almost 70% of the reproductive females. Based on our results, we can guarantee that a female whose body condition is above the line will reproduce, although not all those females below the line are non-reproductive, as a few of those under the line will nest. With this information, we have one more biological indicator to take into account when making management and conservation decisions.

Keywords: Caiman latirostris; K-Fulton; body condition index; crocodile; energetic investment; reproduction; scaled mass index (SMI).

Figure 1

Body condition indices according to body size (snout vent length; SVL) for the 87 females analyzed. The straight lines delimit the body condition of females of a given size that are estimated as strictly reproductive (located above the line) from those that may or may not be reproductive with similar size: (A) Scaled mass index (SMI), without the addition of the estimated weight of their eggs to the breeding females attending the nest; (B) SMI.S, with the addition of the clutch dry weight to the weight of the clutch found attending the nest; (C) K-Fulton, without the addition of the weight of the clutch attending the nest. (D) K-Fulton.S, with the addition of the clutch dry weight to the weight of the reproductive females found attending the nest. The color patterns represent the status of the female, filled circle: Reproductive (R) detected via ultrasound; unfilled circle: Reproductive (R) detected attending the nest; triangle: Non-reproductive (NR). The vertical dotted line represents the size (79 cm SVL) at which 80% of the females below the line were found to be reproductive.