Ripple et al (2014) showed that in many places outside Africa there are only three for four large carnivores today. In contrast, in N America in the late Pleistocene there were at 10-15 large carnivores (lions, cheetah-like cats, wolves, sabre-tooth cats etc). Such numbers of hyper carnivores have been typical for millions of years
E Africa 2.5 myr ago had 17 hyper carnivores (but only 13 now), Yellowstone has around 9. There was an earlier extinction event in Africa, around 2 million years ago. But North America in the Pleistocene was richer in hypercarnivores than East Africa today.
Why was Pleistocene N America so diverse in carnivores?
There had been immigration of lion, hyena and brown bear via Siberia. Bison immigration also may have supported high carnivore diversity.
It is very difficult to get animal abundance data from the fossil record. She looked at tooth wear and fracture. Percent of broken teeth is a good metric of amount of prey in the diet. More broken teeth indicate rare prey. Nice ground testing on modern wolf studies in N America and Sweden. She looked at Pleistocene predators. Much higher proportional breakage of teeth than most model carnivores. This is even true for carnivores that still persist (e.g. coyote and wolf).
This suggests that food was limited for large predators and interspecific competition was more intense than on average for modern ecosystems. Prey abundance was tightly constrained by this abundance of hyper carnivores. But despite this, these populations were quite stable for millions of years. In many cases, prey densities were limited by the predators. This may have made the ecosystem vulnerable by an unusually flexible predator - humans.
Humans are unusual members of the large predator community that are less affected by competition and predation than other species. They have a flexible diet (can switch between foods), they were accompanied by dogs (additional hunting benefit), complex social behaviour, weapons, fire and language. A super predator outside the guild yet having a huge impact. (Ripple and Van Valkenburgh 2012, BioScience).
Human hunting may have triggered a cascade that led to extinctions, forcing other carnivores to eat down the food chain. Humans did not need to kill all the herbivores themselves to trigger Pleistocene overkill.
Analogy with sea in 18th and 19th centuries observed trophic cascade after removal of whales. Great wolves - harbour seals - otters - kelp forests.
What can we learn from the Pleistocene?
It was a resilient ecosystem because there was carnivore redundancy, carnivores could move.
If we add a new predator to an ecosystem there will be consequences for predators and also other prey.
E Africa 2.5 myr ago had 17 hyper carnivores (but only 13 now), Yellowstone has around 9. There was an earlier extinction event in Africa, around 2 million years ago. But North America in the Pleistocene was richer in hypercarnivores than East Africa today.
Why was Pleistocene N America so diverse in carnivores?
There had been immigration of lion, hyena and brown bear via Siberia. Bison immigration also may have supported high carnivore diversity.
It is very difficult to get animal abundance data from the fossil record. She looked at tooth wear and fracture. Percent of broken teeth is a good metric of amount of prey in the diet. More broken teeth indicate rare prey. Nice ground testing on modern wolf studies in N America and Sweden. She looked at Pleistocene predators. Much higher proportional breakage of teeth than most model carnivores. This is even true for carnivores that still persist (e.g. coyote and wolf).
This suggests that food was limited for large predators and interspecific competition was more intense than on average for modern ecosystems. Prey abundance was tightly constrained by this abundance of hyper carnivores. But despite this, these populations were quite stable for millions of years. In many cases, prey densities were limited by the predators. This may have made the ecosystem vulnerable by an unusually flexible predator - humans.
Humans are unusual members of the large predator community that are less affected by competition and predation than other species. They have a flexible diet (can switch between foods), they were accompanied by dogs (additional hunting benefit), complex social behaviour, weapons, fire and language. A super predator outside the guild yet having a huge impact. (Ripple and Van Valkenburgh 2012, BioScience).
Human hunting may have triggered a cascade that led to extinctions, forcing other carnivores to eat down the food chain. Humans did not need to kill all the herbivores themselves to trigger Pleistocene overkill.
Analogy with sea in 18th and 19th centuries observed trophic cascade after removal of whales. Great wolves - harbour seals - otters - kelp forests.
What can we learn from the Pleistocene?
It was a resilient ecosystem because there was carnivore redundancy, carnivores could move.
If we add a new predator to an ecosystem there will be consequences for predators and also other prey.