Biomedical subjects

Hugh Drummond

Publications and source records attributed to Hugh Drummond.

3 recordsLinked to original sources

PubMed2006

Senescent birds redouble reproductive effort when ill: confirmation of the terminal investment hypothesis.

This study reports an experimental confirmation of the terminal investment hypothesis, a longstanding theoretical idea that animals should increase their reproductive effort as they age and their prospects for survival and reproduction decline. Previous correlational and experimental attempts to test this hypothesis have yielded contradictory results. In the blue-footed booby, Sula nebouxii, a long-lived bird, after initial increase, male reproductive success declines progressively with age. Before laying, males of two age classes were challenged with lipopolysaccharide to elicit an immune response, which induced symptoms of declining survival prospects. Reproductive success of immune-challenged mature males fell, while that of immune-challenged old males showed a 98% increase. These results demonstrate that senescent males with poor reproductive prospects increase their effort when those prospects are threatened, whereas younger males with good reproductive prospects do not.

Age Factors↗

PubMed2006

Dominance in vertebrate broods and litters.

Drawing on the concepts and theory of dominance in adult vertebrates, this article categorizes the relationships of dominance between infant siblings, identifies the behavioral mechanisms that give rise to those relationships, and proposes a model to explain their evolution. Dominance relationships in avian broods can be classified according to the agonistic roles of dominants and subordinates as "aggression-submission," "aggression-resistance," "aggression-aggression," "aggression-avoidance," "rotating dominance," and "flock dominance." These relationships differ mainly in the submissiveness/pugnacity of subordinates, which is pivotal, and in the specificity/generality of the learning processes that underlie them. As in the dominance hierarchies of adult vertebrates, agonistic roles are engendered and maintained by several mechanisms, including differential fighting ability, assessment, trained winning and losing (especially in altricial species), learned individual relationships (especially in precocial species), site-specific learning, and probably group-level effects. An evolutionary framework in which the species-typical dominance relationship is determined by feeding mode, confinement, cost of subordination, and capacity for individual recognition, can be extended to mammalian litters and account for the aggression-submission and aggression-resistance observed in distinct populations of spotted hyenas and the "site-specific dominance" (teat ownership) of some pigs, felids, and hyraxes. Little is known about agonism in the litters of other mammals or broods of poikilotherms, but some species of fish and crocodilians have the potential for dominance among broodmates.

Aggression↗

PubMed2003

Buffered development: resilience after aggressive subordination in infancy.

Do aggressive dominance and subordination in vertebrate broods and litters affect development? We examined 1,167 fledglings from two-chick broods of the blue-footed booby (Sula nebouxii), a species in which the first-hatched chick dominates with violent attacks throughout the nestling period and subordinates suffer lower fledging success, but if both broodmates survive, they grow to the same size. There was little evidence that dominant fledglings were more likely to recruit into the breeding population than were subordinate fledglings, and there was no evidence that dominant and subordinate recruits differed in their age, date, brood size, or nest success at first reproduction or in their summed brood sizes or total nest success over the first 5 yr or first 10 yr of life. Compared with dominants, subordinate fledglings were less prejudiced by late hatching and established clutches earlier over the first 10 yr, and subordinate recruits had 33% larger broods over the first 5 yr. However, in broods where both chicks fledged, accumulated reproductive success for chicks up to age 5 yr was similar for dominants and subordinates. Exercising dominance throughout infancy apparently does not fortify a chick for the future and may incur a long-term cost, and suffering violent subordination throughout infancy has little or no prejudicial effect and may even steel a chick for adult life.

Aggression↗