# Size Gynomimicry in the Sanmartinero Creole Bovine of the Colombian Orinoquia

## TL;DR

This study examines whether male and female Sanmartinero creole cattle in Colombia show differences in size, finding some statistically significant differences in body measurements.

## Contribution

The study provides the first evidence of sexual size dimorphism in the Sanmartinero creole bovine using morphometric analysis.

## Key findings

- Statistically significant differences in body measurements were found between male and female Sanmartinero cattle.
- Variables like height at the withers and rump showed the most significant sex-based differences.
- Most size-related variables were biased toward males, though only two were statistically significant.

## Abstract

The external variations between animals of the same species but of different sex are called sexual dimorphism. Variations in size are called sexual size dimorphism. In the creole bovine, the phenomenon of sexual dimorphism has been little studied. The aim of this study was to establish whether sexual dimorphism appears in the Sanmartinero creole bovine, in the department of Meta, Colombia. A total of 21 linear variables were obtained using standard morphometric methods and live weight, from a sample of 94 animals (16 uncastrated males and 78 females) with an average age of 4.3 ± 1.4 and 4.2 ± 2.3 years were measured. Statistically significant differences were found between sexes (p = 0.033) and not by age and farms. The variables that most differentiated males from females were thoracic circumference, body length, height at the withers, height at the rump, dorso-sternal diameter, and horn length. The only variables that presented statistically significant differences were the height at the withers and the rump, with values biased toward males. More studies are needed to understand sexual size dimorphism in the Sanmartinero creole bovine.

Variations in the size of animals of the same species but of different sex are called sexual size dimorphism. The aim of this study was to compare the biometrics between males and females of the Sanmartinero creole bovine, of Colombia, to establish if sexual dimorphism appears in the breed. A total of 94 animals (16 uncastrated males and 78 females, average age of 4.3 ± 1.4 and 4.2 ± 2.3 years, respectively) from three different farms were measured. A total of 21 linear variables were obtained using standard morphometric methods and live weight. A one-way NPMANOVA was used to evaluate between sexes, ages, and farms, a Principal Component Analysis was used to detect the most discriminating variables, and a multivariate regression used age as an independent value. Statistically significant differences were reflected between sexes (p = 0.033) and not by age and farms. The variables that differentiated the most between males and females were those related to size (thoracic circumference, body length, dorso-sternal diameter, height at the withers, height at the rump, and horn length), variables that were biased toward males, although only the height at the withers and the rump were the ones that presented statistically significant differences.