Identifying and protecting spider monkeys in Ecuador

spider monkey

There are estimated to be fewer than 250 individual brown-headed spider monkeys in Ecuador in the wild

Using a combination of GIS modelling and field data, we have identified a priority conservation site for the critically endangered brown-headed spider monkey (Ateles fusciceps) in NW Ecuador.

We have been working since 1995 on the brown-headed spider monkey that is endemic to the NW of Ecuador and southern Colombia. The species inhabits the evergreen humid tropical forests of the Pacific coastal zone and the Andean foothills.

Population decline

With an estimated population of fewer than 250 individual Ateles fusciceps in Ecuador in the wild, the species is considered critically endangered by the IUCN. Population decline is due to hunting and high rates of deforestation that has resulted in the loss of more than 80% of forest cover in the region.

Unfortunately, the ecology and life history of Ateles fusciceps exacerbate the situation. First, these primates are known to inhabit only large continuous areas of primary forest (ie forest of more than 60 years of age). Second, spider monkeys have a relatively low reproductive rate, owing to an extended interbirth interval of 2–3 years. This hinders their ability to recover from population crashes.

In 2000, Ecuadorian legislation banned the hunting and commercial use of Ateles fusciceps. The Convention on International Trade in Endangered Species (CITES) subsequently up-listed Ateles fusciceps to Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning that international trade in the species is comprehensively monitored (CITES 2007).

Spider monkeys have a relatively low reproductive rate, owing to an extended interbirth interval of 2–3 years. This hinders their ability to recover from population crashes

However, the actual impact of these national and international legislative measures on the conservation status of primate populations in the isolated forests of NW Ecuador is unknown. The major challenge to developing a conservation action plan for this species on the brink of extinction has been our dearth of knowledge of it.

Focusing conservation efforts

Geographical information system (GIS) approaches have been a relatively recent addition to the set of tools available to conservation biologists.. GIS is especially useful in identifying regions of potential conservation significance. Thus, in 2000, GIS information on plant diversity and loss of habitat was key to identifying the most threatened regions globally – conservation ‘hot spots’ – that merit special conservation effort. One of these 25 regions is the Ecuadorian Choco – the habitat of Ateles fusciceps.

With GIS, we used satellite imagery to identify current extent of forest; ecological-niche modelling to determine potential primate distribution; and models to predict hunting levels to estimate current distributions of the species. A. fusciceps is a good indicator of habitat quality and hunting levels, with high abundance suggesting priority conservation areas – ‘hotspots within a hotspot’.

Figure showing spider monkey density

Figure showing mean density (with 95% confidence intervals) of Ateles fusciceps with increasing altitude in NW Ecuador

Collecting data

Modelling is useful but we also needed real data from the field to assess the status of A. fusciceps populations in order to initiate effective conservation action. However, there are inherent practical difficulties in studying primates at low densities in isolated and rugged tropical forest terrain.

Because sighting monkeys in dense forest is often difficult or impossible, a number of studies have used auditory methods in population surveys of primates with extensive and regular vocal repertoires. From anecdotal evidence it is known that Ateles fusciceps responds to hunters who mimic their alarm call. As a result, we developed and applied a playback method to assess population numbers on an altitudinal transect from sea level to the altitudinal limit of A. fusciceps.

Modelling allowed us to predict potential distributions and field data collected using the playback method refined these estimates, showing highest densities of the species in the lowlands. We were able to identify a priority conservation site to the west of the existing Cotacachi-Cayapas Ecological Reserve. We have now identified a number of populations in this area, with a particularly healthy group near the community of Tesoro Escondido.

Written by

  • , Lecturer in Conservation Ecology, University of Sussex
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