Many animals capable of deploying chemical defences are reluctant to use them, suggesting that synthesis of toxins imposes a substantial cost. Typically, such costs have been quantified by measuring the elevation in metabolic rate induced by toxin depletion (i.e. during replenishment of toxin stores). More generally, we might expect that toxin depletion will induce shifts in a broad suite of fitness-relevant traits. In cane toads (
Rhinella marina
), toxic compounds that protect against predators and pathogens are stored in large parotoid (shoulder) glands. We used correlational and experimental approaches in field and laboratory settings to investigate impacts of toxin depletion on growth rate and behaviour in cane toads. In free-ranging toads, larger toxin stores were associated with smaller gonads and livers, suggesting energetic trade-offs between toxin production and both reproduction and energy metabolism. Experimental removal of toxin (by manually squeezing parotoid glands) reduced rates of growth in body mass in both captive and free-ranging toads. Radio tracking demonstrated that de-toxined toads dispersed more slowly than did control toads. Given that toxin stores in cane toads take several months to fully replenish, deploying toxin to repel a predator may impose a substantial cost, explaining why toads use toxin only as a final line of defence.
The most prevalent findings in reproductive tracts of 38 laboratory and 17 free-ranging Rhesus female monkeys were vaginitis, cervicitis, metritis, pelvic endometriosis and uterine adenomyosis. Several monkeys had cervical dysplasia and one had a serous cystadenoma. The findings in the two groups were similar although prevalence for several diseases differed. There was a significant relationship between the occurrence of vaginitis, metritis, adenomyosis and endometriosis and gravidity, time since last pregnancy, number of matings, hysterotomies, reproductive ability and reproductive status.
Innovative coconut-opening in a semi free-ranging rhesus monkey (Macaca mulatta): a case report on behavioral propensities