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  • Overview
  • Objectives
  • Skills you gain
  • Costs to Consider
  • Site Conditions

If you can stay for a period of 7 weeks you will have enough time to visit the marine site following 6 weeks of data collection for a dissertation project at the terrestrial site. This can be for research experience or used for your final dissertation project as part of your undergraduate studies. With this course after your first 6 weeks in the forest, you would then be able to move to the marine site to gain your PADI open water dive training certification, or if already qualified, take part in the Caribbean reef ecology course.

Those booking this option, please email expeditions@opwall.com to let them know whether you would like to learn to dive, snorkel or are already qualified.

Sympatric howler monkeys and spider monkeys are large-bodied primates that generally occupy primary forest with large fruiting trees that can provide sleeping sites and sufficient fruit supply (Dunn et al., 2009; Asensio et al., 2012). Spider monkeys are diurnal frugivores that can travel across large areas in search of food. Consequently, ranging and behaviour can vary considerably in relation to fruit availability (Asensio et al., 2012; Pinacho-Guendulain & Ramos-Fernández, 2017; Reyna-Hurtado et al., 2017). Howler monkeys are folivore-frugivores and although diurnal, they exhibit little activity during the day, and spend up to 80% of their day resting (Estrada et al 1999; Pavelka & Knopff 2004). Howler monkey inactivity is likely due to the high percentage of toxin-loaded mature leaves in their diet and fermentative digestion, which are energetically demanding. However, howler monkeys are reported to preferentially feed on ripe fruit when available, which can account for up to 80% of the diet during certain months of the year (Estrada et al. 1999; Pavelka & Knopff 2004). Due their adaptable diet, howler monkeys can live at high densities in relatively small home ranges where they adapt their diet rather than their ranging in response to fruit availability (Reyna-Hurtado et al., 2017).

There are notable sex-differences in the quality of social relationships and the type of social interactions exchanged by male and female spider monkeys (Slater et al., 2009). Unlike other primates, spider monkeys rarely engage in social grooming and have a unique suite of friendly behaviour consisting of embraces, kisses and pectoral sniffs. Rates of friendly behaviour and aggression vary considerably between male-male, male-female and female-female dyads and can provide insight into the strength of social bonds (Slater et al., 2009, Schaffner et al., 2012. Aggression between males is generally rare, and males direct the vast majority of their aggression towards females (Slater et al., 2008). Female aggression also occurs relatively infrequently, but when it does occur it is generally between adult females in the context of feeding (Asensio et al., 2008; Slater et al., 2009). In comparison, howler monkeys interact very little, and indications of social bonds are best determined by patterns of proximity rather than social interactions (Corewyn & Pavelka, 2007). Patterns of proximity indicate that the strongest social bonds within troops are between adult males and females, especially females with young infants (Corewyn & Pavelka, 2007).

A large community of spider monkeys and two troops of howler monkeys can be found in the same geographical area adjacent to the unexcavated ruins of El Ramonal in the Calakmul Biosphere Reserve. Food availability within their home ranges can be assessed using a phenology trail and both species are habituated to human presence permitting behavioural observations of the diet, activity budgets, ranging, habitat use and social interactions. The aim of the long-term study is to understand how each species adapts to fluctuations in fruit availability and to compare differences in behaviour between the two sympatric species.

Extended Dissertation Summary

If you would like to do a dissertation or thesis with us but your university hasn’t started dissertation planning or the project selection process, that’s no problem. You can cancel your expedition with zero cancellation charges up until the 15th of April of if you provide documentation from your university saying that they won’t support completing a dissertation project with us.

Mexico Terrestrial Research Objectives

The Calakmul Biosphere Reserve (CBR) in Mexico is an UNESCO World Heritage Site of Culture and Nature and is part of the largest expanse of neotropical forest north of the Amazon, filled with ancient Mayan ruins and supporting one of the highest biodiversity levels in the world. The CBR is also an extremely important wildlife corridor that is crucial for migrating
birds and mammals with extensive ranging patterns such as jaguar and Baird’s tapir. Over the last 10 years the reserve has experienced a notable reduction in rainfall. Monitoring data on birds, bats, herpetofauna, butterflies, ungulates, felids and primates are being used to evaluate the impact of climate change and changing rainfall patterns on the abundance, ranging and diversity of fauna to help determine when and where mitigation should be used to restore water sources. Data are also used to assess the efficacy of a range of sustainable development projects with buffer zone communities designed to minimise forest encroachment. In addition, there are specialist studies on jaguar and their preferred prey, behaviour of spider monkeys and population demographics of Morelet’s crocodiles.

  • Develop an independent research project and write a formal proposal
  • Collect data from behavioural observations
  • Study fission-fusion dynamics
  • Learn how to organise and analyse large data sets
  • Opwall fee.
  • Cost of international flights into and out of Cancun.
  • Cost of internal travel to and from the start and end point of the expedition, plus any hotels you might require. The standard package costs around £319 or $415.
  • Extra nights’ accommodation in Cancun costs around £72 or $93 (breakfast included).
  • Park entrance fees are £20 or $26.
  • Mexico charges a tourist tax, currently approximately $13 before leaving the country to travel home.
  • Vaccinations and prophylactic medicines – cost can vary depending on your healthcare provider.
  • All prices in GBP or USD unless specified.
  • Standard travel insurance – cost can vary, for 2 weeks it can range anywhere from £40-80 or $40-150.

Most of our volunteers fundraise for their expedition costs. Find out more.

In Mexico it is hot and humid. Temperatures rarely drop below mid 20s even at night. It is unlikely to rain much, but you do get occasional heavy showers during the season.

Fitness level required
Medium in the forest, low on the marine site. There are some reasonably long walks through the forest, terrain varies by camp with some being almost completely flat and others more undulating. On the marine site lower levels of fitness are required (although you will likely be very tired at the end of the day after the in-water sessions).

Creature comforts
Facilities in the forest are basic (sleeping in tents or hammocks in a camp site), with a mixture of dry and trench toilets. There are freshwater showers but water conservation is particularly important to bear in mind. There are some limited opportunities to buy snacks at some forest camps and there is no phone signal at any of the sites. On the marine site the facilities are a little less rustic – you sleep in bunk beds in dormitories about 10 minutes drive from the beach. There is good phone signal and the site is well supplied with shops.


  • Mexico
  • Calakmul

Want to get involved with this project?


Want to get involved with this project?

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