Study Reveals Heightened Threat to Primate Survival as Big Cats Increase Consumption of Monkeys in Degraded Tropical Forests

In the forests of southern Mexico, where human activities like regular wood harvesting and the creation of large clearings for farming or settlements leave a substantial footprint, jaguars and pumas appear to be altering their dietary preferences. New research suggests that in these areas, these big cats are inclining towards incorporating more monkeys into their diet.

Previous research has established that when the typical prey of big cats becomes scarce, these predators adapt by seeking alternative food sources. The observed shifts in the diets of jaguars and pumas, as documented by my colleagues and me, suggest that the populations of their usual prey may be diminishing, or that environmental changes have occurred, making the capture and consumption of primates a more accessible option.

The shift in the dietary preferences of large cats raises concerns about the potential decline of primate populations in the tropical forests of southern Mexico. This change increases the risk of large cats facing food shortages, which, in turn, poses a threat to the stability of the entire ecosystem, potentially leading to the endangerment of these feline predators.

Pursuing majestic felines

The impact of deforestation or alterations caused by logging and hunting extends disproportionately to primates, given that numerous species rely on tall trees for sustenance, shelter, and navigation through the forest. Alarmingly, on a global scale, over 60% of primate species face the imminent threat of extinction.

The transformations occurring in these altered forests also jeopardize the survival of large predators. Gaining insights into the dynamics of these areas can guide the development of more impactful conservation strategies, potentially averting the disappearance of species within these ecosystems.

Situated in southeastern Mexico, the Uxpanapa valley stands as one of the few remnants of tall evergreen forest in the country. Acknowledged for its exceptional biodiversity, the region is classified among the most biologically diverse areas in both Mexico and the world. Within this habitat reside various species, including jaguars, pumas, and two endangered primates: howler and spider monkeys.

Under the leadership of Aralisa Shedden, a research team conducted the inaugural study on primate distribution in the Uxpanapa Valley. Their investigation involved documenting the primate population, identifying their locations, and examining their forest habitat preferences.

A separate team employed the assistance of a specially trained dog to locate scat, or feces, left by large cats. The collected scat was analyzed to extract DNA, allowing for the identification of the species, examination of potential parasites, and insights into the cats’ dietary habits. Microscopic examination of hairs found in each scat, guided by specialized identification resources, facilitated the determination of the prey consumed by these large cats. Each type of animal hair was linked to specific characteristics, including color, pattern, and shape.

Large carnivores play a crucial role in preserving biodiversity and ecosystem functionality by regulating the populations of specific species, such as herbivores that could otherwise damage trees or impede forest regeneration. The presence of these predators serves as an indicator of an ecosystem’s overall health. Understanding the dietary preferences of top predators provides research teams with additional insights into the functioning of an ecosystem.

What their investigation uncovered?

Upon amalgamating the collected data and information, the research team began to discern an unusual phenomenon unfolding.

The scat analysis revealed that primates constituted the most prevalent prey found in jaguar and puma excrement, accounting for nearly 35% of the remains. Additionally, primate remains were more prevalent in scats collected from areas with diminished forest cover. For instance, spider monkey remains were more frequently identified in scats collected in regions with increased human settlements and in forests undergoing regeneration following disturbances.

One potential interpretation is that areas with higher numbers of villages may experience increased hunting and deforestation. In regions where hunting is intensified, the traditional prey preferred by jaguars and pumas may become less abundant. Additionally, regenerating forests may not provide the same level of protection for primates as tall, undisturbed forests. These factors could contribute to the observed higher frequency of large cats preying on spider monkeys in such areas.

Jaguars and pumas tend to target the most abundant prey available. When their preferred prey is scarce, they adapt their diet to include the species they encounter more frequently. The observed pattern with howler monkeys aligns with this behavior: in areas with diminished tall forest cover, remains of howler monkeys were more likely to be present in the scats, suggesting that large cats found it easier to access primates in such environments.

The increased predation on primates by large cats in these areas may be attributed to factors such as reduced tree cover, over-hunting of other prey, and overall habitat loss. Ongoing monitoring of these sites is crucial for gaining a comprehensive understanding of the shifts in the diet of large cats.

The findings underscore the critical role of preserving extensive forest cover to safeguard the survival of primates and other species dependent on forest ecosystems. They also emphasize the pressing need for conservation efforts to mitigate the potentially irreversible impacts of human activities on both primate and large cat populations and the ecosystems they inhabit.

Resources

1. ^NEWSPAPER Shedden, A. & The Conversation. (2023, November 18). Researcher: Big cats eat more monkeys in a damaged tropical forest, which threatens survival of primate populations. Phys.org. [Phys.org]
2. ^JOURNAL Shedden, A., Solórzano‐García, B., White, J. M., Gillingham, P. K., & Korstjens, A. H. (2023). Drivers of jaguar (Panthera onca) and puma (Puma concolor) predation on endangered primates within a transformed landscape in southern Mexico. Biotropica, 55(5), 1058–1068. [Biotropica]
3. ^JOURNAL Foster, R. J., Harmsen, B. J., Valdes, B., Pomilla, C., & Doncaster, C. P. (2010). Food habits of sympatric jaguars and pumas across a gradient of human disturbance. Journal of Zoology, 280(3), 309–318. [Journal of Zoology]
4. ^JOURNAL Estrada, A., Garber, P. A., Rylands, A. B., Roos, C., Fernández-Duque, E., Di Fiore, A., Nekaris, K. a. I., Nijman, V., Heymann, E. W., Lambert, J. E., Rovero, F., Barelli, C., Setchell, J. M., Gillespie, T. R., Mittermeier, R. A., Arregoitia, L. D. V., De Guinea, M., Gouveia, S. F., Dobrovolski, R., . . . Li, B. (2017). Impending extinction crisis of the world’s primates: Why primates matter. Science Advances, 3(1). [Science Advances]