Veterinary session

Out of the 36 currently extant wild cat species 23 are threatened or endangered with extinction in their natural range. The population declines are due to deforestation, loss and fragmentation of natural habitats, and human-animal conflicts. In situ and ex situ conservation efforts are both imperative to protect these species from extinction. Understanding the endocrine status associated with reproductive physiology is crucial for proper captive management practices. Using blood samples for hormonal analysis is contraindicated due to the high risk associated with stress, especially in pregnant animals. All big cats have species-specific reproductive characteristics, such as the length of the oestrus cycle and the possibility of spontaneous ovulation, and therefore every species has to be individually investigated.

In our study we examined the endocrinological status of the female jaguar in ARTIS Amsterdam Royal Zoo, the Netherlands. She was observed daily for signs of oestrus behaviour in order to facilitate successful copulations, while faecal and urine samples were also collected for hormonal analysis. These samples from different stages of a suspected pregnancy were examined for progesterone and 13,14-dihydro-15-keto-PGF2ɑ (PGFM) levels using enzyme immunoassays.

The obtained progesterone values ranged from 0,28 µg/g to 9,61 µg/g in faecal samples, while reached up to 57,56 µg/g in urine samples. While wild cats show a high variability in faecal progesterone metabolite levels, our results are on the low end of concentrations measured in all species of Felidae. However, these values fall close to data already published for jaguars, suggesting that this could be the physiological range for this species. The PGFM values were obtained in a range of 18,11 ng/g to 84,28 ng/g from the faecal samples. Using PGFM as a potential biomarker is still a developing method of hormone-based pregnancy monitoring, and ours is, as far as we know, the second study attempting to work with this hormone. While the pioneering study showed promising results with a small sample size, our results failed to support their hypothesis, that in the late term pregnancy can be confirmed by measuring PGFM in only a few samples.

Our results of two jaguar cubs are self-evident, yet our hormonal analysis fails to either confirm or reject pregnancy. The lack of clear trends is attributed to the limited number of samples, as well as to the lack of species-specific endocrinological knowledge. Future research should include longitudinal monitoring of hormonal changes throughout the entire pregnancy, as well as further optimization and validation of the current methodology.