Coloration anomalies are widespread across the animal kingdom; however, they pass underreported for some taxa or are extremely rare, like in the case of mammals. Three of those anomalies are albinism, leucism, and erythrism, each of which generates atypical colorations in white with white spots and reddish-brown, respectively. Here, we report five cases of coloration anomalies in mammals from Panama: 1) albinism in the Derby’s woolly opossum (Caluromys derbianus Waterhouse, 1841), the lowland Paca (Cuniculus paca Linnaeus, 1766), and the variegated squirrel (Echinosciurus variegatoides Ogilby, 1839). 2) leucism in the Central American agouti (Dasyprocta punctata J. E. Gray, 1842), and 3) erythrism in the northern Tamandua (Tamandua mexicana Saussure, 1860). We discuss some implications of these observations and the importance of gathering this type of data for developing more complex studies in the future.

Albinism, erythrism, leucism, Mammalia, melanin

It is known that color in mammals is almost exclusively due to the presence or absence of melanin present in the skin, hair, and eyes (Hofreiter and Schöneberg 2010; Ortiz-Hoyos et al. 2020). Atypical colorations occur occasionally due to an excess or deficit in the production of melanin in some body parts or the whole body (Acevedo and Aguayo 2008; Abreu et al. 2013). Some of those atypical colorations include melanism, leucism, albinism, and piebaldism (Abreu et al. 2013).

The term melanism is used to refer to blackened phenotypes (Jackson 1997; Nachman et al. 2003); leucism for phenotypes with atypical white patches (Veena et al. 2011); white phenotypes with black eyes (Mitchell and Church 2002; Van Grouw 2006; Steen and Sonerud 2012; Moore and Ouellet 2014); and abnormal pale or discolored colorations (Sage 1962; Snyder 1968; Acevedo and Aguayo 2008; Derlindati et al. 2013). For instance, piebaldism is a form of leucism in which the phenotype is characterized by the presence of abnormally light males (Acevedo et al. 2009). There is still some divergence among some authors, mainly because some of the studies do not take into account the differences between piebaldism and leucism (e.g., Geiger and Pacheco 2006; Oliveira 2009). Overall, the term albinism has been widely used to refer to any type of hypopigmentation, and the term piebaldism refers to phenotypes with white spots (Zalapa et al. 2016), which is inappropriate because piebald is one of several genes that produce white spots (Lamoreux et al. 2010). Moreover, another anomaly in coloration is called erythrism, which is characterized by reddish or reddish-brown coloration in the hair or feathers (Bukaciński and Bukaciński 1997; Pirie et al. 2015).

Although leucism is expected to occur in all vertebrate classes, it is a very rare anomaly in natural populations (Camacho et al. 2022, and references therein). In the case of albinism, the phenomenon is extremely rare in vertebrates, especially in mammals (McCardle 2012), and strongly associated with visual and auditory dysfunctions (Creel 2015). On the other hand, there is a lack of information on the generality of erythrism in mammals, and it seems to be more common in non-mammal vertebrates (e.g., Mačát et al. 2016; West and Allain 2020; Hidalgo-Licona et al. 2023). For this reason, it is important to report these anomalies and gather knowledge about the generality of these phenomena and associated variables between mammal species to better understand their occurrence. Here, we present cases in five species of mammals in Panama: albinism in the Derby’s woolly opossum (Caluromys derbianus), the lowland Paca (Cuniculus paca), and the variegated squirrel (Echinosciurus variegatoides); erythrism in the northern Tamandua (Tamandua mexicana); and a case of leucism in the Central American agouti (Dasyprocta punctata).

At the Eustorgio Méndez Zoological Collection, we found nine samples of Caluromys derbianus (five males and four females); eight of them were collected between 1960 and 1970 within the Panamanian territory, and one sample from Colombia was collected in 1967. One of the individuals was albino and was collected in 1970 near the village of Aguacate (8.957630871, -79.98264601, Capira, province of Panama Oeste, Figs 2, 3a). It is worth mentioning that we found an individual with grayish-brown coloration, similar to the subspecies Caluromys derbianus pallidus, collected in 1967 (Fig. 3a). At the MVUP, we found seven males and seven females, collected in Panama between 1980 and 1993; all of them showed the typical reddish-brown coloration for the species. Besides our report, other five species of marsupials on the American continent have been reported with some form of coloration anomaly, including another anomaly that generates a yellowish coloration called xanthochromism (Table 1).

We report the first case of albinism for Cuniculus paca in Panama, a male weighing 10 kg and 66.7 cm in length (Fig. 3b). Besides, we report the first case of albinism in Echinosciurus variegatoides, which was observed on June 6, 2018, by two biologists who shared the picture with us (Fig. 3c).

The observation of two tamanduas (Tamandua mexicana) with erythrism would expand the geographical range where the anomaly has been observed in the past (Fig. 4).

Regarding the agouti, to our knowledge, this is the first report of leucism for Dasyprocta punctata (Fig. 5). This individual was photographed multiple times and often in the presence of individuals with the typical coloration (Fig. 5).

Figure 3. 

Coloration anomalies in mammals from Panama. Morphotypes of Caluromys derbianus at COZEM showing an albino (bottom), the typical reddish brown (center), and an atypical greyish individual (a). Albino individual of Cuniculus paca that was hunted by locals at the village of Aguacate (b) and albino individual of Echinosciurus variegatoides observed near the Pacora river (c see text for coordinate details). Photo credit: Aracelys De Gracia C. and Roberto Vergara E.

Figure 4. 

Individuals of Tamandua mexicana showing erythrism. A rescued juvenile at Capira (a) and an adult on the campus of the Universidad Tecnológica de Panamá (b). Photo credit for photograph b: Instagram account of the UTP.

Figure 5. 

An individual of Dasyprocta punctata with leucism on Cebaco Island. The top-right square shows the same agouti consuming corn kernels, together with individuals showing the typical coloration for the species.

Overall, color anomalies in mammals are probably underreported in the literature, and here we present five cases of mammals from Panama, contributing to understanding the frequency of the occurrence of these anomalies in wild mammal populations. Here we report three novel cases of coloration anomalies in mammals: albinism in C. derbianus, albinism in E. variegatoides, and leucism in D. punctata.

For instance, it seems that atypical colorations are spread across the order Didelphimorphia (McCardle 2012; Abreu et al. 2013; Eckhardt et al. 2013; Cuxim-Koyoc et al. 2019; Ortiz-Hoyos et al. 2020; Vanstreels et al. 2021; Cotts et al. 2023a; Freire-Filho et al. 2024). However, all these reports were made for species within the genus Didelphis, and here we report the first case of albinism for the genus Caluromys.

In the case of rodents, albinism has been reported in at least 66 species in the world (Romero et al. 2018; García-Casimiro and Santos-Moreno 2020). Our report of albinism in C. paca expands the range of distribution of the phenomenon for the species, which was first reported in Mexico in 2017 (García-Casimiro and Santos-Moreno 2020). Albinism is the only coloration anomaly that has been reported for lowland pacas, and further work can provide deeper insights into the occurrence of this anomaly in the region.

Albinism in squirrels seems to be geographically spread, with reports from Asia (Sayyed et al. 2015), Central Europe (Hoekstra 2004), Siberia (Serebrennikob 1931), and North America (Ferron 2013). Here, we report the first case of albinism for E. variegatoides, a species distributed from Mexico to Panama, and therefore contribute to reporting the occurrence of albinism in rodents in the tropics, which is significantly underrepresented in the literature (Romero et al. 2018). In the case of agoutis, partial albinism was reported for the Azara’s agouti in Brazil (Dasyprocta azarae Lichtenstein, 1823, Oliveira 2009), leucism in the black agouti from Ecuador (D. fuliginosa Wagler, 1832, Mejía Valenzuela 2019), albinism in D. punctata from Honduras (Elvir-Valle et al. 2021), and we report the first case of leucism in D. punctata. The occurrence of leucism (and albinism) in island populations like Cebaco would suggest that inbreeding and low genetic variability are potential triggers (Prado-Martinez et al. 2013; Brito and Valdivieso-bermeo 2016). Moreover, although atypical colorations like albinism are expected to be disadvantageous in terms of survival chances against predators (Vignieri et al. 2010), it is unclear whether leucism could also be selected against as drastically as albinism. Leucistic phenotypes can present defects that impair sensory organs and nerves (Fleck et al. 2016), which should disfavor their fitness and survival. Related to survival, a security guard in Cebaco mentioned that leucistic agoutis were common in the area, a predator-free site. Therefore, in the absence of predators, this abnormal coloration does not seem to impair their survival as a result of some form of related pathology. Further long-term studies could evaluate whether coloration anomalies are more frequent in isolated populations, isolated from predators, and try to disentangle the genetic and ecological drivers of these anomalies.

Regarding the tamanduas, this genus shows a large range of coloration anomalies on the continent (Cotts et al. 2023b). By adding up our data and previous studies (Cotts et al. 2023b), we indicate that erythrism is the most frequent coloration anomaly in tamanduas in Central Panama. In fact, besides erythrism, only leucism has been observed for T. mexicana in Peru (More et al. 2021). An overall estimation of the occurrence of these anomalies in mammals is needed if future studies intend to better understand the variables that drive the occurrence of the anomalies. However, we are aware that such a task is difficult without accurate estimations of the population size of the species of interest.

For that reason, more accurate methods for monitoring cryptic mammals could provide better estimates of the rarity of coloration anomalies. Assembling a large dataset of their occurrence across taxa, geographical regions, and potential explanatory variables can provide significant information for more complex studies (e.g., systematic reviews and meta-analysis). For instance, in squirrels, melanism is significantly higher in urban areas, possibly due to lower predation and abiotic factors (Cosentino and Gibbs 2022).

Coloration anomalies are rare in mammals; therefore, it is important to report them with the goal of understanding the commonality across taxa and consequently the mechanisms driving their occurrence. Here, we provide four novel observations, including albinism in a marsupial and two rodent species from Panama, besides a case of leucism for the Central American agouti. Additionally, we observed two cases of erythrism in the Northern Tamandua that, together with previous observations, suggest that it is the most common coloration anomaly for this tamandua species in Central Panama. Further work is needed to better understand the genetic and ecological factors driving the expression of these anomalies and their implications.

We thank Juan M. Pascale and Aydee Cornejo for allowing access to the collection from the Eustorgio Méndez Zoological Collection. We also thank Ricardo Pérez and Idis Batista at the Vertebrate Museum of the University of Panama for allowing access to the collection. We are thankful to Aracelys De Gracia C., Roberto Vergara E., and Environmental Solutions Panama SA for sharing their observations of the albino squirrel. We thank the Departamento de Gestión Ambiental, Dirección Nacional de Gestión Energética, Ambiental e Ingeniería Aplicada de la Universidad Tecnológica de Panamá, Máximo Higuera, and Maritza Rodríguez for sharing the photographs of the tamanduas. We also thank Bethzaida Carranza for her help during the drafting of the manuscript. We thank the Sistema Nacional de Investigación for funding this project (DG) and the Smithsonian Tropical Research Institute for access to the WOS search tool, and the University of Bristol for access to the Scopus search tool.