Is too much exercise bad for monkeys?
October 30, 2012
The howler monkey diet is as fruity as possible and as leafy as necessary. They gorge on figs, when available, and chomp on tree and vine leaves when fruit is scarce. As forests become increasingly fragmented and lianas become more common, howler monkeys eat more fallback foods, including lianas, to survive – and spend more energy doing so.
In southeastern Veracruz, Mexico, researchers, including STRIs Stefan Schnitzer, compared the eating habits of mantled howler monkeys in fragmented forests to howlers in healthier jungles. The degraded-forest dwellers not only ate more lianas than their counterparts, but they also ate more species of liana. Howlers in healthier forests left many of these species off the menu.
The research, published in Biotropica with Jacob Dunn of the University of Cambridge as lead author, showed that howlers that were more reliant on lianas also spent significantly more time traveling to find food, and less time foraging at any given spot once they arrived.
The study raises questions about how well fallback food meets the needs of howlers. Since their foraging strategy is known to be based around minimizing energy expenditure, such increases in activity may have negative effects on their health and fitness. Indeed, forthcoming work by Dunn, Cristóbal- Azkarate and colleagues in the International Journal of Primatology demonstrates that increases in travel time are related to increases in the stress hormone cortisol.