EXTRA CREDIT STRESS SCENARIOS – For each of the following gr…
EXTRA CREDIT STRESS SCENARIOS – For each of the following graphs, explain WHAT IS HAPPENING to raise the glucocorticoids (cortisol) level of the animals. Note that you must go beyond what is already stated, which may require that you speculate on the cause of the glucocorticoids rise. (Worth 1 point each) HOATZINS – Mullner and colleagues (2004) investigated the effects of ecotourists on the reproductive success of hoatzins (Opisthocomus hoazin) and on the hormonal status of their chicks and juveniles by comparing birds from undisturbed and from tourist-exposed nests. Hoatzins build simple platform nests on branches overhanging the water. The modal clutch size is two eggs and the incubation period lasts 32 days; usually only one chick survives. If not disturbed, hatchlings stay in the nest 14–20 days and then begin to climb into the surrounding foliage. As an adaptation to life in inundated forests, hoatzin chicks prior to fledging show an extraordinary escape behaviour when approached by a predator: they jump into the water and may dive 5–15 m in an attempt to escape. With the help of their wing claws they climb another tree, but do not return to their nest site. Instead, the adults normally find the young and feed them until fledging. The authors concluded that wildlife observation in the rainforest is not as harmless as often thought. Fig. 3. Stress-induced corticosterone secretion of hoatzin chicks from undisturbed and from tourist-exposed nests. Each point represents the mean ± SE for the concentration of plasma corticosterone and sampling time for (a) nestlings from undisturbed and tourist-exposed sites, respectively and (b) juveniles from undisturbed and tourist-exposed sites, respectively.