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Lessons from vervets and macaques. MSc ACSB module 2006/07 AC Session 3. Vervet monkey alarm calls. Cheney & Seyfarth: " How monkeys see the world “ Vervet monkeys (tree + ground living monkey, Africa) Predators = Leopard, Monkey-eating Eagle, Python, + baboons, etc, and 3 calls

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Lessons from vervets and macaques l.jpg

Lessons from vervets and macaques

MSc ACSB module 2006/07

AC Session 3

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Vervet monkey alarm calls

  • Cheney & Seyfarth: "How monkeys see the world“ Vervet monkeys (tree + ground living monkey, Africa)

  • Predators = Leopard, Monkey-eating Eagle, Python, + baboons, etc, and 3 calls

    • Eagle gets a Cough,

    • Snake gets a Chutter

    • Leopard gets a Bark

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Vervet alarm-call responses

  • Behave appropriately when they hear one of these calls (run down from treetops / walk carefully / run up into trees)

  • Do they know what messages the calls carry? (e.g “There is an Eagle, / a Snake, / a Leopard”)

  • Film response to plausible taped call; no real caller whose behaviour might give hearers a clue to the right response

  • 3 responses are given in appropriate contexts using just the information in the call itself, showing the monkeys are responding to the acoustic signals, not just to caller’s concurrent behaviour

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Vervet calls on www

  • http://www.wjh.harvard.edu/~mnkylab/media/vervetcalls.html

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Vervet alarm calls provide information…

  • … about environment, not about signaller’s motivational state (e.g. different levels of fear) – equivalent of words for the 3 predators?

  • Nearer to language than the displays considered last time – is call-use learned c.f. word-use?

  • Are monkey vocalisations acquired/learned?

    • Not in squirrel monkey - innate.

    • Perhaps in X-fostered Japanese & rhesus macaque food-coos

    • Learning probably contributes in vervets

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Ontogeny of vervet predator calls

  • Vervet infants give alarms to appropriate class of stimuli, but too wide a spread of targets within each class

    • “Leopard” to many large ground animals

    • “Eagle” to birds of all sorts

    • “Snake” to sticks and other long thin objects

  • As grow up, they focus alarms down on the real predators, the class-members that spell danger

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Vervet call development (3)

Probability of adult alarm call

after infant has given eagle alarm

call – high only to Martial eagle + 1 other sp.

Infants give fewer wrong and more adult-like responses to alarm call playback as they grow older

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Vervet call development (4)

  • Narrowing down of call-triggers may depend on response from adults: take up and repeat alarm to real hazards, ignore it to a harmless stimulus

  • Responses to alarm calls not fully adult

    • Initially respond after looking at an adult which has started to respond

    • More often show adult-like response when near mother than when mother has wandered away

  • Vervets use wrrr-call to indicate threat from another group; experience shapes its correct use over 1st two years of life (earlier if more frequently in contact with other groups)

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Involuntary or voluntary?

  • High ranking vervets call more often, and are more often the first to call; but don’t scan for predators more often. So subordinates must also scan and detect predators, but omit call

  • Females call more readily if kin present

  • Captive males call more when female companion(s) than when companion is male

  • Never call “eagle” when should say “leopard”

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Is this alarm call system unique?

  • Calls provide info about dangers, not level of fear

  • Vervet monkey grunts (Cheney & Seyfarth)

    • Can't be distinguished by ear by humans

    • 4 types: Dom>Sub, Sub>Dom, Move Into Open, see Another Group

  • Difference in response to taped grunts indicates monkeys can separate them, appropriate information conveyed, e.g.

    • MIO : listener looks towards loudspeaker

    • AG: looks away towards where loudspeaker points

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Vervet grunts

16 acoustic parameters from one female: 82% correct classification of her calls and others' calls

Spectrographically distinct but cannot be distinguished

by ear by humans

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Rhesus macaque screams

  • Rhesus & pigtail macaque screams studied by Gouzoules

  • Rhesus has 5 types of scream – code for

    • Rank of the opponent

    • Whether a relative (safer) or non-kin (risky)

    • Whether or not any physical contact

  • Pigtail has 4 types of scream

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Rhesus screams (2)

  • High rank, contact

  • Low rank, no contact

  • Relative, or

    • High rank, no contact

  • Relative

  • High rank, no contact

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Interim conclusions

  • In Vervet alarm call system, information is encoded in specific calls; coding is partly pre-wired but is refined by experience

  • Several other call systems which communicate environmental information

  • Kitui used the leopard call (sans leopard) to halt a fight that his troop were losing – but then walked across ground repeating the call, which made it plain to humans that there was no real danger

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What information is in a call?

  • Do primates lump-together different calls that refer to the same thing?

  • Habituation

    • Do primates learn to ignore specific calls, or to distrust a mental state (eg fear) in the caller?

    • Are changes in risk tied to a particular threat?

  • Do callers aim to inform, or to trigger a specific response?

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Rhesus food calls

  • 4 food calls

    • Warble, Harmonic Arch (Good food)

    • Coos, Grunts (low-quality food)

  • S1 and S2 initially elicit orientation

  • Habituate S1, then test S2, where S2 may be a different signal for same quality of food, or a different signal for different-quality food

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Hauser’s results

  • Hauser, 1998, Anim Behav 55, 1647-1658

  • Habituate response to one HQ food call:

    • Eliminates response to other HQ call

    • Leaves intact response to LQ calls

  • Habituate response to one LQ food call:

    • Leaves intact responses to HQ food calls

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Cheney & Seyfarth - Vervet

  • Inter-group calls:

    • Wrr (low arousal – just spotted) & Chutter (high arousal – scrap going on or likely)

  • Habituation paradigm:

    • Test Chutter; habituate Wrr (same #); re-test Chutter

    • Decreased response if all 3 stimuli for same hazard, from same #, not if different monkeys’ calls used

  • Implications:

    • know that A and B represent the same threat, conclude that this # has become unreliable about other groups

    • No decrement if calls represent different threats

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Superb staring alarms

  • Aerial and ground predator alarms

  • Test starling alarms: habituate vervet eagle alarm; test starling alarms again

    • Decreased response to starling eagle alarm

    • No decrement for starling ground predator call

  • Have learned to be sceptical about (any) warnings about aerial predators, not just habituated to vervet coughs specifically

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What does caller aim to achieve?

  • In Cameroon, vervets attacked by feral dogs

    • Dogs trigger ‘leopard’ alarm, troop runs into trees

  • Elsewhere, hunted by men with dogs + guns

    • Leopard alarm would attract attention and a shot

    • So dogs trigger a quiet call that allows troop to flee silently

    • Monkey link signals to the action that the signal needs to achieve

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Limits on understanding

  • Kitui used a leopard-call to stop a fight (deception?), but then walked across ground showing that there was probably no leopard – none of the hearers noticed the incongruity

  • Vervets also can’t recognise other indirect cues to danger – e.g., snake track on ground, or antelope carcass stored in tree (which signals that a leopard is nearby)

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References – session 6

  • Cheney & Seyfarth (1992) Behavioral and Brain Sciences, 15, 135-147 (commentary 147-182)

  • Cheney & Seyfarth (1990) How monkeys see the world, Ch. 3-6.

  • Seyfarth & Cheney (2003) Meaning and emotion in animal vocalizations. Annals of the New York Academy of Sciences, 1000, 32-55.

  • Hauser (1997) The evolution of communication. Ch. 5, 7