An international team of scientists described three cases of hunting a Sumatran orangutan female on large slow lorises (Nycticebus coucang coucang).
Much has been said about the role of meat in human evolution. No matter how unpleasant it may be for some vegetarians … it is great, this role. But when did the turn to meat take place, and how did it come about? It is believed that, first of all, our ancestors should have had stone tools for cutting prey (and not for hunting, since the early hominids were probably scavengers).
Some specialists, such as a primatologist Richard Wrangham, believe that the transition to a meat diet was impossible without the use of fire.
If we take Homo erectus (which supposedly needed to consume about 2500 kilocalories per day) and the rate at which modern chimpanzees eat meat (about 400 kilocalories per hour), it turns out that erectus should have spent half 12 -hour day!
In short, there is no way without heat treatment. We know that meat-eating is practiced by some other primates, such as capuchins and baboons. The hunting behavior of chimpanzees is well studied. Of course, animal food is not the basis of their diet.
Why would they hunt at all?
On this score, as many as 5 hypotheses were put forward:
1.the hypothesis of lack of food, 2. the hypothesis "meat in exchange for sex", 3.the hypothesis of excess nutrition, 4.the hypothesis of social association of males, 5. the hypothesis of enlargement of the survey.
Hypothesis 1 ("lack of food") is mentioned most often. It seems to be logical: chimpanzees hunt "out of hunger", in a season when their traditional food - fruits and foliage - becomes scarce. Oddly enough, the facts do not support this hypothesis. On the one hand, chimpanzees do hunt actively during dry seasons.
On the other hand, at least 3 studies have shown the opposite: the hunt took place against the backdrop of an abundance of fruit! (which speaks in favor of hypothesis 3 - "excess nutrition"). In the chimpanzee communities of Gombe and Ngogo, the abundance of food led to an increase in the size of groups - like, here it is, "social association of males" (hypothesis 4).
But in the Kanyawara community, hunting behavior increased during the harvest seasons, even if the group size did not change. At the same time, the males shared meat with the females, but did not receive any sex in return (which means that hypothesis 2 does not work). Hypothesis 5 - "enlarged view" cannot be discounted. It has been shown that chimpanzees hunt more often in open woodlands, where visibility is better and the view is farther than in a continuous forest.
And the orangutans go there too
Not so long ago, it was found out that the orangutans of Sumatra also sometimes hunt. True, apparently, they do this very rarely (and for the orangutans of Borneo, such behavior has not been recorded at all). The main object of hunting for orangutans is slow lorises.
If in chimpanzees it is mainly males that hunt, then in orangutans the picture is different: out of 5 individuals seen for this activity, 4 are females and only 1 male. In total, from 1997 to 2009, 9 cases of orangutans hunting for slow lorises were observed.
The authors of the article, just published in the International Journal of Primatology, 2007-2008. personally observed 3 cases of orangutan hunting. The researchers carefully recorded all the details, and even filmed the process on video!
In all 3 cases, the same adult female (named Yet) acted as the hunter, and her teenage daughter (Yeni) helped the hunter to eat the prey. The hunt always happened like this: Yeth deviated from her usual route, climbed a tree (where the victim was) and threw the loris down, and then went down and finished off the animal with a bite in the head. Apparently, this way of hunting allows the orangutan to avoid the troubles associated with the poisonous saliva of the lory.
Although the mother ate the prey with her daughter, she was in no hurry to share; the initiative has always come from Yeni. Mother only graciously allowed the young orangutan to participate in the meal, and in some cases even offered some resistance. The slow loris they ate together weighed about 800 g.
How do orangutans find their prey?
Since in all cases Yeth turned from her usual path for hunting, it can be concluded that she acted purposefully, i.e. meeting lori was not a coincidence. Slow lorises are secretive nocturnal creatures; during the day they sleep, hiding in a hollow or in a crack in a tree.
Perhaps the orang-utan was specifically looking out for places suitable for sleeping lorises. In addition, Yeth could find prey by scent marks with which these primates mark territory.
Why do orangutans hunt?
Next, the researchers speculate about which of the 5 known hypotheses (listed above) is appropriate for the case of orangutans. The authors honestly warn that the sample is, of course, very small, so conclusions should be drawn with caution.
The hypotheses "meat in exchange for sex" and "union of males" immediately disappear (as they say, "thanks, Cap!"). Orangutans live in a tropical rainforest, where foliage tightly covers everything around them all year round - so the "enlarged view" hypothesis also does not work. But the variant of "lack of food" is quite probable: all the previous known cases of eating meat by orangutans occurred in low-yielding years.
Therefore, the authors specifically checked what is the correlation between the amount of food resources (fruits) and the incidence of loris hunting (for all episodes for which this information is available). Observations confirmed that orangutans actually hunted significantly more often during periods of fruit shortage.
Chew - do not chew …
The authors calculated how fast (in grams and in calories per hour) orangutans eat meat. It turns out that they do this twice as slow as chimpanzees: 161 g or 185 kcal per hour, versus 348 g or 400 kcal per hour in chimpanzees.
And according to some reports, chimpanzees can eat meat at a speed up to 2 kg per hour! Perhaps the reason is that chimpanzees are significantly more social than orangutans. Chimpanzees are hunted in a group; Nearby, as a rule, there are many who want to take away the prey, so you need to chew quickly and quickly.
According to researchers, orangutans, in terms of the massiveness of their jaws and some features of their teeth, can be more comparable to Australopithecines than chimpanzees, whose dental system is closer to Homo erectus. Let's leave this statement on the conscience of the authors.
Therefore, the obtained data can be tried to be transferred to Australopithecus and calculated: how long would Australopithecus have to chew meat in order to gain its daily calorie intake (with a mixed vegetable-meat diet).
Australopithecus Africanus, presumably, was supposed to receive 1202-1507 kcal daily. If we take the figures obtained for the orangutan (185 kcal per hour), and assume that Australopithecus received 25% of all calories from meat (and 75% from leaves, fruits, insects, etc.), then he had to chew meat daily within 2 hours.
It is assumed that Australopithecines lived in groups (like chimpanzees and unlike orangutans). If they hunted together, then the time spent on getting food was reduced. It is also possible that in the process of socialization, hominids began to chew faster (as we observe in chimpanzees). Thus, if in early hominids meat made up a quarter of the diet, then the time spent on eating it should not be very long.
After all, our ancestors did not immediately switch to meat!For non-specialized carnivores, consuming too much animal protein is generally dangerous. In short, it will be possible to speak about the need for heat treatment of food only when it is proved that in early Homo and Homo erectus, meat accounted for more than 25% of the diet, the authors conclude.