How baboons and like-size, coexisting gazelles differ in their most basic anti-predator strategies, part 2

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Sympatric Thomson's gazelle and olive baboon show the great variation in pace of life in mammals, hence the different potentials of prey species to support predators.

These two species both

  • weigh about 20 kg,
  • have similar metabolic rates, and
  • bear about a dozen offspring per lifetime.

However, the gazelle breeds three-fold as rapidly as the primate does, as shown by

  • time from conception to earliest birth (16 months vs 4 years),
  • time from birth to weaning (6 months vs 18 months),
  • time from birth to social maturity (males: 3 years vs 9 years), and
  • time between subsequent births (9 months vs 25 months).

Accordingly, Thomson's gazelle lives only a third as long as does the olive baboon (15 years vs 45 years). (Note that the olive baboon lives about as long as does Hippopotamus amphibius, despite the great difference in body mass.)

I infer that this gazelle, a ruminant, spends energy more rapidly (3-fold) on reproduction and growth than does this monkey - making this energy available to predators.

The productivity and the abundance of gazelles both help to sustain the cheetah.

Thomson's gazelle eats grass and other herbaceous leaves, which are

  • abundant compared to the fruits, tubers, flowers, and small animals eaten by the olive baboon, and
  • digested more thoroughly by the ruminant - with its thoroughly fermentative digestion - than by the monogastric primate (partly because Thomson's gazelle rechews its food by night, while the olive baboon sleeps).

Then same density of population of gazelles and baboons can support 3-fold the offtake by predators in the case of this gazelle - hence the potential for a specialised carnivore, living at small densities of population, in the form of the cheetah. This baboon seems as limited as marsupials in its productivity and ability to support predators.

Posted on July 10, 2023 12:33 AM by milewski milewski


Values for olive baboon vs Thomson's gazelle:

Body masses similar
Gestation periods similar
Number of offspring per lifetime 12 vs 13 (similar)
Lifespan from birth 45 years vs 15 years (3-fold)
Time from being conceived to giving first birth 4 years vs 16 months (3-fold)
Time from birth to weaning 18 months vs 6 months (3-fold)
Female sexual maturity ?4.5 years vs ?1 year (perhaps up to a 6-fold difference)
Male social maturity 9 years vs 3 years (3-fold)
Interbirth interval about 25 months vs about 9 months (2-fold)

Posted by milewski about 1 year ago

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