The wild lowland paca (Cuniculus paca), an often overlooked yet ecologically significant mammal of the Amazon, has recently been the focus of an enlightening research study on its reproductive parameters, providing vital insights into its ability to withstand hunting pressures. Conducted by a team of seasoned researchers headed by Hani El Bizri at the Manchester Metropolitan University and Instituto de Desenvolvimento Sustentável Mamirauá (IDSM), the study leverages a 15-year hunter participatory program and presents groundbreaking findings on the generation length (GL) of the wild lowland paca, a pivotal metric for determining sustainable hunting practices.

DOI: 10.1016/j.anireprosci.2019.04.009


Generation length (GL) is a critical measure used to gauge the capability of a species’ population to endure different levels of human-induced hunting without leading to a depletion in their numbers. It is calculated by considering the age of sexual maturity, first reproduction, and reproductive senescence. However, for many wild mammals, these data are elusive, making accurate GL estimations a challenge.

In this detailed study, published in the Animal Reproduction Science journal [1], a sample of 119 female genitalia obtained over a considerable period provided researchers with pertinent data about the reproductive lifespan of the elusive wild lowland paca.

Age at Sexual Maturity and First Parturition

One of the standout revelations from the research is the identification of the body mass at which pacas reach puberty, found to be 5.46 kg on average. The study extrapolates this data to suggest that sexual maturity in wild lowland pacas is achieved around 4 months of age, a significantly earlier timeline than those derived from previous studies that were largely based on the assessment of captive animals. Moreover, the empirical evidence suggests first parturition, that is, the occurrence of the first birth after the onset of sexual maturity, typically happens 9 months post-birth.

These findings contest longstanding notions about the reproductive mechanics of the species, most notably by indicating that first reproduction occurs much earlier in their lifespan than previously estimated.

Reproductive Senescence

The study also explored the concept of reproductive senescence, which refers to a decline in reproductive functionality with age. Interestingly, the researchers found no evidence to suggest a fall in parturition rates as the animals grew older. This insight has resulted in a recommendation; to use the average age of mature hunted pacas in the determination of the most effective harvesting rates to ensure their survival and ecological presence.

Implications for Sustainable Harvesting

The underlying implication of these findings lies in harvest sustainability. By having a more accurate understanding of when pacas reach sexual maturity and continue to reproduce, hunters and wildlife managers can devise better-informed strategies that ensure the maintenance of robust paca populations in the Amazon.

El Bizri and colleagues advocate for the adoption of similar in situ reproductive studies for other tropical species subject to human hunting. The authors stress the enhanced accuracy of reproductive variable estimates obtained from animals in their natural habitat versus those derived from individuals in captivity.


The relevance of this study is multifaceted, contributing not only to ecology and conservation but also providing a template for future wildlife reproductive research. The following references were pivotal to the research:

1. El Bizri, H., Rocha, H. R., et al. (2019). Age at sexual maturity, first parturition, and reproductive senescence in wild lowland pacas (Cuniculus paca): Implications for harvest sustainability. Animal Reproduction Science, 205, 105-114. DOI 10.1016/j.anireprosci.2019.04.009.

2. Mayor, P., Bodmer, R. E., & Lopez‐Bejar, M. (2011). Reproductive performance of the wild lowland paca (Cuniculus paca) in the Peruvian Amazon. The Veterinary Journal, 190(2), 217-221. DOI: 10.1016/j.tvjl.2011.03.008.

3. Bodmer, R. E., & Robinson, J. G. (2004). Evaluating the sustainability of hunting in the Neotropics. In People in Nature (pp. 299-323). Columbia University Press. ISBN: 9780231132516.

4. Keuroghlian, A., & Eaton, D. P. (2008). Removal-rate estimates and variability in ecological studies of Neotropical peccaries. Tropical Conservation Science, 1(4), 245-259. DOI: 10.1177/194008290800100403.

5. Fa, J. E., Ryan, S. F., & Bell, D. J. (2005). Hunting vulnerability, ecological characteristics and harvest rates of bushmeat species in afrotropical forests. Biological Conservation, 121(2), 167-176. DOI: 10.1016/j.biocon.2004.04.019.


The lowland paca plays an integral role in the Amazonian ecosystems, and its population dynamics are heavily influenced by reproductive parameters. The study provides an essential groundwork for reassessing the sustainable hunting guidelines currently in place, potentially altering our approach to biodiversity conservation and our understanding of tropical fauna reproductive ecology. It heralds a call for more on-the-ground, species-specific data collection, offering a clearer projection of the future for species affected by human consumption.


1. Sustainable hunting lowland paca
2. Reproductive parameters Cuniculus paca
3. Amazonian wildlife conservation
4. Generation length wild pacas
5. Tropical species reproduction studies