Predicted population trends for Cozumel Curassows (Crax rubra griscomi): empirical evidence and predictive models in the face of climate change

Abstract

We assessed the current conservation status and population trends of Cozumel Curassows (Crax rubra griscomi), a critically endangered and endemic cracid of Cozumel Island, Mexico. Distance sampling was used to estimate the population size in 2005 and compare it with a previous estimate in 1995. Population viability analysis (PVA) was used to model population trends, considering ecological and environmental conditions prevailing in 1995 and 2005. Additional PVA models were constructed using different hypothetical scenarios to assess the effects of particular factors and management strategies on population trends. We estimated a population size of 372 ± 155 curassows in the island's tropical semideciduous forest, before two hurricanes hit Cozumel Island in 2005. PVA modeling predicted a steep decline in population size in the ensuing decades as a result of an increased frequency and intensity of hurricanes related to global climate change, and an observed female bias in the sex ratio likely caused by a higher mortality rate for adult males. We recommend urgent management actions for the long‐term conservation of Cozumel Curassows, including a ban on hunting, eradication of the feral fauna, particularly dogs, and implementation of a captive‐breeding program to supplement the wild population.

Camera traps provide valuable data to assess the occurrence of the Great Curassow Crax rubra in northeastern Costa Rica

“…There is no reliable hunting data from across the corridor, but it is well known that the Great Curassow is an important hunting target in Costa Rica [6,8,10], Guatemala [31] and Mexico [11]. The observed sex ratio was biased toward females, which is similar to the observed sex ratio in Cozumel [32]. This sex ratio suggests that the population in the corridor may be hunted because breeding males have higher mortality rates than females due to their easy detection while displaying during the breeding season.…”

Population size assessment of the Endangered red-billed curassowCrax blumenbachii: accounting for variation in detectability and sex-biased estimates

“…Using distance sampling we estimated a population size of 264 individuals at the Reserve, and accounting for sex-specific detection probabilities our corrected population estimate is 325. The estimated density of red-billed curassows in our study (1.3 individuals per km 2 ; corrected estimate 1.6 individuals per km 2 ) is similar to that of other curassows, such as Crax rubra griscomi (1.02; Martínez-Morales et al, 2009), Pauxi tuberosa (1.11–1.65; Haugaasen & Peres, 2008) and Crax alberti (1.66; González, 2004). However, higher densities have been recorded for other species; for example, Pauxi pauxi (4.8; Setina et al, 2012), C. globulosa (3.4; Hill et al, 2008) and Crax fasciolata (4.66; Desbiez & Bernardo, 2011).…”

“…Few studies report skewed sex ratios in cracids but those that do usually report a female skew attributed to hunting of booming males by poachers (Sedaghatkish & Brooks, 1999; Martínez-Morales et al, 2009). Hunting has been one of the main threats to the red-billed curassow throughout its range (Sick, 1997; Delacour & Amadon, 2004) and is still common, especially in southern Bahia.…”

Secondary forest is utilized by Great Curassows (Crax rubra) and Great Tinamous (Tinamus major) in the absence of hunting

“…Given their striking bill coloration and easy detection during mating displays, males are more easily detected and killed by hunters (Pardo et al 2017). Consequently, where hunting is present, sex ratios are typically skewed toward females (Martínez-Morales et al 2009, Pardo et al 2017. Absence of hunting may also release mesopredators (e.g., coatis, capuchins, and racoons) that prey on nesting females.…”