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Department of Evolutionary Anthropology

Standardized field methods

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For the Indonesian version of the methods click here:

Instructions for collection of behavioral data on orang utans

During the Orangutan Culture Workshop (February 2002) in San Anselmo, USA, a document on orang utan data collection standardisation was drafted based on the experience of all participants. Every field project will have different main questions and will thus have to make choices about which data to collect in detail. However, it is hoped that observers in all field sites will collect basic data in a standardised way, so that these can be used for comparison between different sites.

The following general field rules for the orang-utan project in Tuanan (Kalimantan Tengah) were based on the standardisation document. We have added examples of vocalisations and cultural variants. Phenology plots and littertraps are used according to the standardisation document.

For questions contact Dr. Carel van Schaik (vschaik* or Dr. Maria van Noordwijk (vnoord*

  1. Write down everything you find interesting, unusual or remarkable.
  2. Repeat name focal(s), date and observer on every page, including map(s).
  3. When in doubt about (instantaneous) Activity count to 5 - note first activity sustained for more than 5 seconds (for example when moving inside a food patch).
    When in doubt use the hierarchy: Soc > M > F > R
  4. Write in the “sosial” column also special activities and features of the “cultures and traditions checklist”.
  5. Morning nest: Write down when observer arrives at the nest as well as the start of the active period = when the focal becomes active on the nest (sits up, plays with infant etc.) or leaves nest. Whenever the focal has moved to another nest during the night, or if data were incomplete on the previous night’s nest, please fill in the sarang pagi info on the day nest sheet.
  6. Evening nest: Write down activities until the focal lies down (golek) on nest Fill in the Evening Nest (sarang sore) or the Day Nest checklist (sarang siang). Definitions of nest additions: • Pillow (bantal): a pile of twigs or big leaves at one side of the nest on which the focal puts its head when lying down. Blanket (selimut): a cover made from branches or leaves covering the body, not covering the head Lining (alas): a layer made on the nest from leaves or twigs on top of which the focal lies down. Roof (atap): a construction made from branches or twigs by the focal above and covering the nest (don’t forget to write down whether there is rain or bright sun: sunroof!) Bunk nest: if the focal rests in a nest directly under another nest (either old or just made) this is called a bunk nest. Write details. Carry Tarantang leaves: focal picks and carries Tarantang leaves (or note if other species) towards the nest from other tree.
  7. Patch Residence: Make a vertical line in column “jenis/patch”, ending when focal leaves the patch. End with __. Different trees of the same species less than 10 m apart are considered a single patch.
  8. When possible measure feeding rate, enter on focal page 4/5 for focals and mothers; on mother-offspring page 6 for offspring. Make sure that feeding rates always refer to same set of activities as “F” on focal sheets, so that you can extrapolate to total intake.
  9. Long Calls: fill out checklist for every call given by the focal and for every call heard by observer (and focal).
  10. Map: On every map: • draw exact route indicate location on every whole and half hour indicate location of morning nest (X), or start observation (o) indicate location at evening nest (X) or end observation due to other reason (o) indicate location of food patches used for > 10 minutes



  1. 1. Party: whenever the focal is within 50 m of other orangutans this is a party. Note the identity (or at least age-sex class) of party members + time start & end on focal page 4/5. Always note the presence of (dependent) offspring as well (so: not just name of mother, but always add name of infant if infant is with mother). Please also note if the association (<50m between individuals) ended when/because another individual joined the party. IF THE OTHER ORANGUTAN IS NOT BEING FOCALED PLEASE WRITE DOWN ALL ITS BEHAVIOUR (AND VOCALISATIONS) THAT APPEARS INTERESTING, ESPECIALLY WHEN DIRECTED TO THE FOCAL.
  2. The distance between party members is recorded on the “5min party sheet”: every 5 minutes write which party members are at 0-2 m, 2-10m and at 10- 50 m distance. Unless offspring is clinging to the mother all the time, do this for both mother and offspring relative to other party members.
  3. Approach and Leave: Note on focal page 4/5 which party members spend time at < 10 m and at < 2 m from the focal; do the same for non-clinging offspring with other party members. Keep track of who approaches and who leaves the 2 m and 10 m radius and at what time.
  4. When focal travels in/with a party, including mother - offspring parties, always note in the “jenis/patch” column who leads: write name + dulu.
  5. When focal feeds in/with a party, including mother - offspring parties, always note in the “jenis/patch” column who enters and feeds in patch first: write name + dulu.
  6. 6. When the focal is in a food patch note the following situations in the “item” column: • feeding tolerance (ftol + who): focal and other are feeding in same patch < 10 m apart; also write this down for non-clinging offspring with regards to other party members. co-feeding (cof + who): focal and other are feeding from same item close together or take turns; includes “tolerated theft” (one holds item, other takes - note who “owns) food sharing (share): active giving of food by one to other (note who does what) add details in sosial column mouth-to-mouth feeding (mtm), also mouth-to-hand (mth), hand-to-mouth (htm) and hand-to-hand (hth), this happens mostly between mother and infant, • For all these events make sure the appropriate approach/leave checklist is filled out. • Also note when there is clear avoidance of food tolerance and co-feeding and refusal of food sharing despite begging/ attempts to take food from other. top
  7. When focal makes nest while in a party, including mother - offspring parties, always note on the appropriate nest form who starts making a nest first and the distance between the nest of the focal and nest(s) of the party members and whether in the same tree or not.
  8. Describe ALL social interactions from beginning to end as complete as possible (including who approached/initiated interaction and who ended/departed first) in “sosial” column on focal sheet using behavior elements as defined in the list (if behavior is not on list describe in detail!) - note time and duration. (When not enough space continue on extra sosial sheet(s)).
  9. For all sexual interactions, describe in detail who approaches and initiates contact, who makes vocalizations, whether there is intromission, who thrusts, whether ejaculate is visible afterwards and if so where. In addition always note with duration whether: • female resists successfully or attempts to resist (forced copulation or attempt), describe whether she struggles (may include bite, slap, pull etc.) and whether female becomes passive/cooperative later onfemale is passive, allows intromission, but without active cooperationfemale is cooperative, positions herself to facilitate intromissionfemale is active: she initiates mating and she thrustsa third individual (often offspring) interferes by getting in between, pulling, slapping etc. Remember that the focal’s activity during these interactions is always SOC.
  10. Social Play: For all social play (SP as activity), write down identity of the partner in the “jenis/patch” column. Note in the “sosial” column time + duration, kind of play (wrestle, chase, other), position (on nest?), postures (hang from hands/feet/ each other?) and other details.



  1. Follow all rules for parties, in addition every half hour fill in the distance between mother and offspring, whether they are in the same tree or in different trees and what type of weather it is (sunny, cloudy, heavy rain, drizzle) on the checklists on focal sheets: distance classes: • 0 = contact<2 = no contact but less than 2 m<5 = more than 2 m but less than 5 m<10 = more than 5 m but less than 10m<20 = more than 10 m but less than 20 m<50 = more than 20 m but less than 50 m>50 = more than 50 m (out of sight)
  2. Approach-Retreat = Mendekati-Menjauhi: on the special sheet note every time the distance between mother and offspring changes at the 2m or 10 m level, becoming more or less than 2 m, or becoming more or less than 10 m. Always note who caused this change, if observed. (Imagine two concentric bubbles around the mother, one of 2 m radius and one of 10 m radius, - as soon as the offspring passes through these bubbles fill out the checklist).
  3. Nest: always note whether the offspring makes its own nest or stays in the mother’s nest. Fill in checklists for every nest used (morning, day and evening)
  4. Travel: when mother forms a bridge for the offspring to cross between 2 trees write “bridge” in the items column; when mother started to leave a patch, but then rests and “waits” for her offspring to come to her to be carried, write “wait” in items column.
  5. Initiative toward contact: when mother-offspring contact is established, note whether the mother collected the infant or the offspring made the contact (unless same as <2 m event).
  6. Many activities are compatible with either being supported by the mother or being in contact with the mother. If that happens, combine them in the acitivty column, with C first, such as C/D, C/M, C/F or C/TF, C/R, C/Rs, C/AP, C/SP. When the infant is trying to feed on an item, by playing around with it in its mouth this should be noted as TF (Try Feeding).



Move M all locomotion, usually between trees/patches, if within patch movement should last for more than five seconds and not be simultaneously with feeding
  Mq quadrupedal walking on horizontal substrate
  Mb Brachiating
  Mt Treesway
Rest R sit, lie, stand, hang for more than 5 seconds, not doing anything else
  Rs sit or lie on nest (= sarang)
Feed F processing, gathering, ingesting food items, some movement (less than 5 seconds duration) within a patch consistent with these goals may be included
  Ffr feed on fruit note ripe/unripe in item column (if clearly feeding on seeds, OK to make new subcategory F sd)
  Fsd feed on seeds (still note ripe/unripe in item column)
  Ffl feed on flowers; note details in item column
  Fyl feed on young leaves
  Flv feed on mature leaves
  Fveg feed on other vegetative plant parts, note details in item column
  Fins feed on insects, note kind in item column
  F bk feed on bark
  Foth feed on something else, describe in item column
  Fw drink water, note from where in item column and how: directly with mouth, drip from hand, drip from leaves, cupped hand etc.
  TF Only for young offspring: trying out food / tasting without really eating; add same items as for F
Suckle D only for immatures: drink milk from mother
Nest N build nest; always note special features (roofs, repair old nest, etc.) - use checklist for night nest (+ nest-list for mother-offspring)
Social Soc all social interactions. Write kind in item column (sex, agonistic, groom, long call or display if directed at other orangutan); give details in sosial column, including how interaction ended
Social Play SP social play with a partner; write kind in item column (wrestle, chase); note details in sosial column and include position (on/above nest, hanging, upside down, etc.) (Remember appropriate approach/leave entries)
Auto play APO
Solitary object play: “nonfunctional” manipulation of objects Solitary movement play: repetitive movement such as twirling, swinging etc
Cling C only for immatures: being carried clinging to the mother’s body, note whether mother supports offspring with arm or leg in item column (Note that Cling is not an exclusive category and may be used in combination with other compatible activities; see #6 Rules for Mother-Offspring)

If in doubt use hierarchy Soc > M > F > R


0 1 2 3 4



These elements are to be used for a description of all social interactions, also between mother and offspring, in the “sosial” column on the focal sheets. Write Vocalizations and Display in the item columns next to activity, give details in social section.

Agonistic elements

in response to a ‘neutral” approach, other one shows signs of fear (submissive mips) and retreats
active displacement fast approach, may include touch or enter into nest resulting in retreat of the approached individual
chase pursuit over more than 10 m or into other tree
flee fast retreat from other individual
flee towards approach and stay close to more dominant individual after third individual approached/threatened
fight whole body wrestle
display sway, drop (or throw) branches; push over dead tree trunks; make clear whether directed at other orangutans or at observers

Other Social elements

kiss mouth to mouth touch (“smell”)
embrace at least one arm touches shoulder/back of other individual
groom skin/hair care (with fingers while looking at this)of other individual; describe details: which body part, wound
watch close attention to action of other e.g. feeding, manipulating, tool-use; describe details and distance (appropriate approach/leave checklist should also be filled out)
look away look away from (“ignore”) other’s action at close range
bridge form a bridge between trees to let smaller individual transfer
beg outstretched hand to other, with or without vocalization
collect infant  

food transfer

tolerated theft individual who collected food item allows other individual to take (part of) it; common from mother to offspring but also seen in other dyads. Food transfer can go ‘mouth to mouth’, ‘hand to hand’, mouth to hand or hand to mouth
active hand-to-hand individual who collected food item actively takes initiative to give some of it to other individual


masturbate sexual self stimulation with hands or tools (if with tools describe!)
sex investigate sniff or touch with mouth or fingers the vagina/penis of other
copulation attempt no intromission achieved
copulation intromission achieved, thrusting by male and/or female

Other behavior elements

scratch scratch with fingers or toes, describe body part
symmetrical scratch with both hand scratch corresponding body parts
autogroom Skin/hair care of own body, with fingers while looking at this
penile erection  
pilo-erection fluffed out fur
throat poach inflation  
bulging lips  
temper tantrum wild repetitive movements, often with screaming/crying, mostly by dependent immatures; describe details and context