Biology subjects

Hohmann, G.

Publications and source records attributed to Hohmann, G..

2 recordsLinked to original sources

bioRxiv2022

Transition to siblinghood causes substantial and long-lasting physiological stress reactions in wild bonobos

In mammals with a slow ontogeny, the birth of a sibling marks a major developmental transition. Behavioral studies suggest that this event is stressful for the older offspring, but physiological evidence for this is lacking, and it remains unknown whether the birth of a sibling is stressful beyond mere weaning stress. Studying transition to siblinghood in wild bonobos, we investigated physiological changes in urinary cortisol (stress response), neopterin (cell-mediated immunity), and total triiodothyronine (metabolic rate), and related them to behavioral changes in mother-infant relationship and feeding (suckling, riding, proximity, body contact, independent foraging). With siblings birth, cortisol levels increased fivefold in the older offspring and remained elevated for seven months, independent of age. This was associated with diminished immunity but not with behavioral or metabolic changes. Our results indicate that transition to siblinghood is stressful beyond nutritional and social weaning and suggest that this effect is evolutionary old.

evolutionary biology↗

bioRxiv2021

In vivo deciduous dental eruption in LuiKotale bonobos and Gombe chimpanzees

Existing data on bonobo and chimpanzee dental eruption timing are derived predominantly from captive individuals or deceased wild individuals. However, recent advances in noninvasive photographic monitoring of living, wild apes have greatly expanded our knowledge of chimpanzee dental eruption in relatively healthy individuals under naturalistic conditions. We employ similar methods to expand on this knowledge by reporting deciduous dental eruption ages in living, wild bonobos and chimpanzees from LuiKotale, Democratic Republic of the Congo and Gombe National Park, Tanzania, respectively. Deciduous dental eruption ages in our sample generally fall within the range of variation previously documented for captive chimpanzees. We also found substantial variation in deciduous canine eruption timing, particularly among bonobos. One bonobo had a deciduous canine present by 227 days old while another did not have a deciduous canine present at 477 days old. As more data accumulate from these populations, future studies should consider sources of variation in deciduous canine eruption timing and relationships with other aspects of life history.

evolutionary biology↗