Sensory Ecology



Detailed Description

Action heroes are usually defined by having some exceptional ability, like ultra-sensitive hearing or x-ray vision. In reality, you don’t have to be a superhero to have heightened sensory perceptions. Sometimes, all you just need is a good enough reason to evolve a characteristic – and usually, that reason is improved fitness. Primates have evolved a number of adaptations to process their surroundings, relying on olfaction, taste, vision, and audition. Disentangling the extent to which each species relies on each of these areas of sensory perception can be complicated, particularly in the wild.

We are tackling this subject among Neotropical primates through multiple projects, each based on the ability of the primate to produce a signal and that of conspecifics or heterospecifics to detect it.

Current Projects: Summer 2019

Project 1: Who am I?

Chemical signaling in mammals is achieved by transmitting information through secretions (both volatile and non-volatile) contained in urine, saliva, scent-marks, feces, and tears. Although primates, in general, have moved away from a strong reliance on olfaction over vision, odor has a significant advantage as a signal in that it can persist even in the absence of the signaler. However, the bulk of primate studies on olfaction have focused on scent-marking, and very few investigations have been made into the response of a conspecific to a specific signal. Even fewer still have achieved these goals in the wild. 

This project will utilize the incredible advantage that the wildlife handling team has earned in the mark-recapture program of tamarins to test to see if tamarins can reliably distinguish signals in conspecific urine on the basis of gender, familiarity, and breeding status. By the careful collection of fresh urine samples during the handling program, we can conduct controlled experiments in which animals awaiting release at the end of the day can participate in voluntary experiments based on a system of simultaneous discrimination, in which their behavioral responses to two cues are judged in comparison to each other. Each trial will involve the presentation of urine samples from familiar/unfamiliar, same/different sex, and primary/secondary/nonbreeders of the same/different sex on swabs. Video recordings will note how much attention animals pay to each swab and will allow for the decoding of investigative sequences post-trial.   

Project 2: Fruit dispersal signals

Broadly speaking, the “evolutionary arms race” of the co-evolution of plants and their dispersers has resulted in some fascinating examples of symbiotic relationships in the natural world. Plants have evolved fleshy, colorful, sweet-smelling fruit to attract bats, birds, and primates to consume them. At the same time, seeds of these fruits are often protected in a hard, bad-tasting coating, to prevent dispersers from actually destroying them. In the end, we see a system in which, for the most part, plants and their dispersers live in relative harmony.

All fruit tend to fall into one of two categories: those that indicate their ripeness by odor and those that do so by color (a third category that signals by both odor and color also exists!). In general, bats (which are more dependent on olfaction than vision) tend to disperse fruits that are odorous when ripe, while birds tend to disperse fruits that are colourful (red/orange/etc.) when ripe. 

In the case of the tamarins, females display an X-linked color vision trait that gives them trichromatic vision (for some animals, heterozygotes at that allele), while males tend to me universally dichromatic. This lets us predict that the dichromatic animals within this population would rely on their sense of smell to detect ripe fruit, over their sense of vision, while the opposite would be true for trichromats. 

In this project, we will present individually identifiable animals for whom we have biological samples that can be tested for trichromacy in the lab using genetics with a choice when they come down to feeding stations utlised in the mark-recapture program. They will be able to view a tray of naturally ocurring fruit in the rainforest that consists of unripe, medium-ripe, and really ripe fruit. Ripeness in each case will be verified on each fruit with a fruit tester (which tests how hard a fruit is), a jaz spectrophotometer (which quantifies the color of the fruit), and a photograph against a colour palette shot with a specialised camera from which we can quantify luminance. In addition, in 2017 we were able to investigate the chemical composition of each fruit species using a portable mass spectrometer. In each experiment we will calculate the rate of food intake of each animal per ripeness category, and correlate that with their colour vision status and the fruit characteristics above. We predict that the trichromats will be more successful with bird-dispersed fruit, while the dichromats will be more successful with the bat-dispersed fruit. 


Research assistants on this program will delve into the field of sensory and cognitive experiments in a unique field setting in which animals either voluntarily approach “experiment” stations or are presented with stimuli moments before being released after the annual capture of the group for health screening. To learn more about our mark-recapture program, please see here. 

Generally speaking, experiments are conducted from early morning to late afternoon at several different field locations, followed by a short break and subsequent data entry or decoding in the evening.  Free time is scheduled into each week for assistants to pursue other interests and sightseeing activities (oxbow lakes with river otters, palm swamps with anacondas, canopy tower, and tagging along with other FPI research programs).

At the end of this program, you will be able to:

  • Design an experiment
  • Record focal behavioral data
  • Work with video recording equipment
  • Complete basic video edits
  • Understand relational databases
  • Perform basic behavioral data analyses
  • Recognize all 11 species of primate at Los Amigos
  • Distinguish species-specific vocalizations
  • Gain a general knowledge about rainforest ecology


We are currently recruiting participants with the following requirements.  If you are uncertain if you are eligible, contact us to confirm.

  • Must be at least 18 years of age by the time the training program begins
  • Must demonstrate a grounding or strong interest in physical anthropology, animal behavior, zoology, or psychology
  • Previous field experience is not required, but previous research experience (either outdoors or in the laboratory) will be a plus
  • Must be able to justify why this program is important to you and what you hope to gain from it
  • Must be able to provide a letter of recommendation from a source that can substantiate your competency and skills
  • Must be unafraid of insects, reptiles and the jungle in general
  • Must be in good physical condition, with the capability to walk 4 miles a day while carrying field equipment
  • Participants will not be discriminated against for medical conditions they might have if we determine that being on this project will not pose an immediate risk to their health.
  • Willingness to adjust your schedule to primate daily activity patterns. This can require waking up early, sometimes by 5 am, and going to bed early.
  • Due to the nature of the work and weather constraints, participants MUST be willing to be flexible about their days off. Assistants will typically have one-two days off per week; however, we cannot guarantee a set schedule and breaks are normally divided into half-days.
  • Participants must sign waivers of liability for this project and for the field station before their participation in the project is finalized
  • Participants must be willing to maintain long hours in the field, but also return to complete data entry in the evening.

Recent Projects: 2014 – 2018

Sight, smell or taste?

Neotropical primates they have an interesting sex-linked, color vision phenomenon.  Excluding howler monkeys, male platyrrhines are all dichromatic, meaning they lack the ability to see all three primary colors.  On the other hand, about half of all the females have trichromatic vision, just like most humans (with a few exceptions).  We can design experiments in the field that test which senses primates use to select ripe fruit, and we would expect the dichromatic females to adopt similar foraging strategies as the males, but the trichromatic females should behave differently if variation in vision does in fact influence foraging efficiency. We predict that a dichromatic primate that has trouble seeing the color differences between ripe and unripe fruit might compensate by honing another skill, such as olfaction or taste. At our site, our mark-recapture program utilizes feeding platforms to habituate primates to traps, and this phenomenon provides us with the perfect opportunity to test trade-offs in sensory perception in the wild.

Alarm Call Awareness

The evolution of language is a fascinating aspect of human biology that can be used as a benchmark for the study of nonhuman primate communication. In the wild, primates have complex vocal repertoires that conspecifics understand, but what of heterospecifics? Can an emperor tamarin understand the vocalizations of a saddleback? Does a specific vocalization mean the same thing to both species? Or can each only understand a word or two of the other’s phrasebook? At our site, we have a population of sympatric tamarins that are exposed to multiple predators in the presence of which they make alarm calls. Each type of alarm call – aerial, terrestrial, or predator-specific – evokes a different suite of behaviors in tamarins nearby. Disentangling these conversations in the context of predator-prey interactions is the goal of this project. We will be conducting playback-experiments at rare and specific intervals in order to examine the ability for each species to respond to the other’s alarm calls.

Scent-marks as Signals

Primates communicate using olfactory signals in two ways, via scents produced by their scent glands and those deposited in their urine.  Combinations of these secretions are applied on substrates in a variety of ways, can be directed towards others, and can code for a range of information such as age, sex, development status and sexual proceptivity. In this project, we are interested in determining which signals animals emit and how they are received.

In addition, we are also looking at a different kind of signal – skin pigmentation. Primate coat colors can vary subtly across their lifetimes and during the year. Other portions of their anatomy, including scent-glands and genitalia, can also change in color in correlation with changes in developmental status.



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Program dates: June 3 – July 30, 2019
Start dates: June 3, June 10, June 17, June 24, July 1, July 8
Minimum commitment: 3 weeks
pplication deadline: April 14, 2019
Program fee: $1350; $450 each additional week



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Primary Investigators

This project began in 2014, and the primary investigators working on it have included Mrinalini Watsa, Amanda Melin, Lais Moreira, Alice Poirier, Rebecca Chen, and Gideon Erkenswick. They represent Washington University in Saint Louis, the University of Missouri-St. Louis, University of Aberdeen, Anglia Ruskin University, and the University of Calgary.