Chimp & See Talk

Nutcracking

  • AnLand by AnLand moderator

    As @MimiA said that out of context questions are okay, I have one that bothers me for quite some time.

    We've seen in the earlier sites a lot of nutcracking, partly with bigger stones or heavy wood branches, and one of the aims of the project is to study this tool use behavior in chimps. I am wondering since being here what difference does the tool use actually make. So, I understand that the nuts (I think, coula nuts here) are too hard to crack them open with e.g. the teeth, but using the stone tools is also energetically costly. What would the chimps miss (in terms of energy intake and dietary composition) without this ability to crack the nuts open with tools and feed on them. Could they substitute for the calories? (I guess that is context dependent, so let's say for the Tai chimps.) What is the net gain? Is it really worth it or a nice-to-have? (Maybe also considering the time it takes to learn this skill.)

    I cannot really find a concise answer to this. Thanks!

    Posted

  • Lyndi23 by Lyndi23 scientist

    Being able to use a tool in an efficient way is always a energetic benefit. For example Coula nuts are very rich in fat and protein and chimpanzees can gain up to 3000 kcal per nut-cracking session, which is an enormous part of their daily calory intake. Additionally tool users are able to create a foraging niche for themselves where they can exploid food sources that remain unaccessalbe to other animal species (this is the case for other chimp tool use as well, not just nut cracking). Female chimpanzees share the nuts they crack open generously with their dependent offsprings. Therefore young chimps are already attracted to the task from a very early age on. During the learning phase I would think that youngsters actually put more energy in than they get out (they can afford this though as their mother still covers necessary energy input). They will all eventually become skilled nut crackers and then it is definitely worth it.

    Posted

  • MimiA by MimiA scientist, moderator

    Thanks @Lyndi23 (you may know her as Lydia Luncz who recently won the Otto Hahn Medal for her amazing nut cracking and chimpanzee culture work)! eg: http://www.cell.com/current-biology/abstract/S0960-9822(12)00318-1

    @AnLand - you may also find this paper interesting: http://www.eva.mpg.de/psycho/pdf/Publications_2009_PDF/Tennie_Call_Tomasello_2009.pdf

    Its by our colleague and good friend Claudio Tennie - who I disagree with on this topic 😉 - but it gives you some insights into why complex behaviours and cultural traits are important for understanding human evolution and why tool use goes beyond what we traditionally think of as adaptive behaviours (ie: its not just about nutritional content).

    A few other relevant papers for the topic are:
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3890823/
    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385679/

    Posted

  • AnLand by AnLand moderator

    Thanks to both of you. But I still do not understand what it would mean if they could not open the nuts. If I follow your description of up to 3000 kcal per nutcracking session, it is a huge percentage of their daily energy intake (from the estimates I found, it is the daily calory intake). So, my question is still: what would it mean for their foraging efforts if they could not crack the nuts? And as you said, there are chimp communities that do not crack nuts. These then have to fill the caloric gap in others ways that are apparently possible as well. Is nutcracking (so: tool usage) just one way or really the better way to meet your energy needs and macronutrients?

    Posted

  • Lyndi23 by Lyndi23 scientist

    There are many other chimpanzee populations that do not nut crack and they are doing fine. The survival of the Tai chimps also does not depend on nut cracking either. That would be very dangerous for them in an unpredictable eco-system like the forest. There are some years with extremely bad or no nut production and they can not rely on that food source. They then eat other stuff (fruits, leaves, insects, meat, ...). So to answer your question, nut cracking is just one way to meet the energy needed, yet a very efficient one. Hope that helps!

    Posted

  • AnLand by AnLand moderator in response to Lyndi23's comment.

    Thanks @Lyndi23, yes that's what I wanted to know. I do not question the importance of nutcracking and tool usage in general, but I am not really clear how that relates to other - non-tool usage - ways of "foraging". (And yes, my question was only related to the energetics - calories in vs. calories out - and the percentage of energy they are getting (on average) from tool use in contrast to other feeding sources. I will look for more information on this. )

    Posted

  • AnLand by AnLand moderator

    In case others are interested too. I found an answer to my question. Coula nuts "are a major food source, comprising of 4.7% of the total Taï diet." (This is a group average over many years of observations, not for each individual.)

    I found it in this paper: Robert C. Power, Domingo C. Salazar-García, Roman M. Wittig, Martin Freiberg, Amanda G. Henry
    Dental calculus evidence of Taï Forest Chimpanzee plant consumption and life history transitions. Scientific Reports, 19 October 2015, DOI: 10.1038/srep15161 (They compare calcified dental plaque remains to observational feeding records and discuss what one can learn from dental calculus about diet, weaning age and - as nutcracking is a learned behavior - about cultural transmission. Here is a link to the press release: http://www.mpg.de/9708096/chimpanzees-dental-calculus-diet. Paper can be found here: http://pubman.mpdl.mpg.de/pubman/item/escidoc:2223592:1/component/escidoc:2223590/Power_Dental_SciRep_2015.pdf)

    Posted