BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofitpublishers, academic institutions, research libraries, and research funders in the common goal of maximizing access tocritical research.

Ecology of the Mexican Red-Bellied Squirrel (Sciurusaureogaster) in Michoacán, MexicoAuthor(s): Nicolás Ramos-Lara and Fernando A. CervantesSource: The Southwestern Naturalist, 56(3):400-403. 2011.Published By: Southwestern Association of NaturalistsDOI: http://dx.doi.org/10.1894/N02-RTS-11.1URL: http://www.bioone.org/doi/full/10.1894/N02-RTS-11.1

BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in thebiological, ecological, and environmental sciences. BioOne provides a sustainableonline platform for over 170 journals and books published by nonprofit societies,associations, museums, institutions, and presses.

Your use of this PDF, the BioOne Web site, and all posted and associated contentindicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use.

Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should bedirected to the individual publisher as copyright holder.

ECOLOGY OF THE MEXICAN RED-BELLIED SQUIRREL (SCIURUSAUREOGASTER) IN MICHOACAN, MEXICO

NICOLAS RAMOS-LARA* AND FERNANDO A. CERVANTES

Departamento de Zoologıa, Instituto de Biologıa, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-153,

Mexico, Distrito Federal 04510, Mexico

Present address of NR-L: Wildlife Conservation and Management, School of Natural Resources and the Environment,

University of Arizona, Tucson, AZ 85721

*Correspondent: ramosln@yahoo.com.mx

ABSTRACT—We report observations on feeding and nesting behavior, reproductive condition, andactivity patterns of the Mexican red-bellied squirrel (Sciurus aureogaster) during 2000–2002 in an oak-pine (Quercus-Pinus) forest south of Patzcuaro, Michoacan, Mexico. Squirrels fed heavily on seeds ofpines, oaks, and dogwoods (Cornus), and rarely cached food. Squirrels used leaf nests for nesting anddid not use tree cavities. Squirrels had year-round breeding activity and were more active in earlymorning and before sunset; however, daily activities were noticeably reduced during hot and sunny daysor during strong winds. Squirrels had two color phases: gray-white and melanistic.

RESUMEN—Reportamos observaciones sobre el comportamiento de alimentacion y anidacion,condicion reproductiva y patrones de actividad de la ardilla mexicana de vientre rojo (Sciurusaureogaster) durante 2000–2002 en un bosque de pino-encino (Pinus-Quercus) al sur de Patzcuaro,Michoacan, Mexico. Las ardillas se alimentaron fuertemente de semillas de pino, encino, y corno(Cornus), y raramente ocultaron alimento. Las ardillas utilizaron nidos de hoja para anidar y noutilizaron cavidades de arbol. Las ardillas tuvieron una actividad reproductiva todo el ano y fueron masactivas temprano por la manana y antes del atardecer; sin embargo, las actividades diarias se redujeronnotablemente durante dıas calidos y soleados o durante vientos fuertes. Las ardillas tuvieron dos fasesde color: gris-blanco y melanica.

The Mexican red-bellied squirrel (Sciurusaureogaster) is native to Mexico and southwesternGuatemala (Thorington and Hoffmann, 2005).In Mexico, the species occurs on the Gulf andPacific coastal plains from Tamaulipas to Tabas-co on the east and from Colima to Chiapas onthe west, inhabiting a wide variety of forestsranging from tropical scrub and broadleafformations of the hot lowlands to cold and wettemperate cloud forests of oaks (Quercus) andconifers in the highlands (Musser, 1968). As with

many species of tropical tree squirrels (Ko-prowski and Nandini, 2008), a dearth of infor-mation exists on their biology and ecology(McGuire and Brown, 1973; Brown andMcGuire, 1975; Ceballos and Galindo, 1984;Ramos-Lara and Cervantes, 2007). Althoughthe species is not listed in Mexico under anycategory of risk (Secretarıa de Medio Ambiente yRecursos Naturales, 2002), Mexican red-belliedsquirrels recently have been included in the RedList of Threatened Species (least concern) by the

THE SOUTHWESTERN NATURALIST 56(3):400–403

400 The Southwestern Naturalist vol. 56, no. 3

International Union for the Conservation ofNature ( J. L. Koprowski et al., www.iucnredlist.org). There is a need for more informationconcerning the basic ecology of this species.

During November 2000–May 2002, we col-lected information on feeding and nestingbehavior, reproductive condition, and activitypatterns of Mexican red-bellied squirrels duringa study of nest-site selection (Ramos-Lara andCervantes, 2007), in a small portion (100 ha) ofthe oak-pine (Quercus-Pinus) forest ca. 7.5 km SPatzcuaro, Michoacan, Mexico (19u27929.10N,101u36941.60W; elevation 2,340 m). Dominantspecies of trees were Quercus candicans, Q.crassipes, Q. laurina, Q. obtusata, Pinus pseudostro-bus, Clethra mexicana, Cornus disciflora, Styraxramirezii, Symplocos prionophylla, and Ternstroemiapringlei. During 2001, mean monthly precipita-tion in the region was 3.83 mm (68.45 SD, n 5

6) for the dry season (November–April), and160.95 mm (6108.54 SD, n 5 6) for the wetseason (May–October), with a mean annualtemperature of 15.06uC (62.53 SD, n 5 12),according to information provided by ServicioMeteorologico Nacional. Each month, we tra-versed the same dirt roads and trails in search ofleaf nests (Ramos-Lara and Cervantes, 2007),and opportunistically recorded information onthe ecology and behavior of Mexican red-belliedsquirrels. The absence of other species of treesquirrels in the study area facilitated identifica-tion and observation of squirrels. We randomlyplaced 10 nest boxes (Barkalow and Soots, 1965)in mature trees ca. 4 m above ground to obtaindata on reproduction. During 30 April–2 May2002, we collected six Mexican red-belliedsquirrels (three adult males, two adult females,and one juvenile male) using a 12-guageshotgun; sex, age class, reproductive condition,and body mass were recorded. Squirrels wereprepared as museum specimens and depositedin the Coleccion Nacional de Mamıferos of theInstituto de Biologıa, Universidad NacionalAutonoma de Mexico, in Mexico City.

We observed Mexican red-bellied squirrelsfeeding on seeds of pines (P. pseudostrobus), oaks(Q. candicans, Q. crassipes, Q. laurina, and Q.obtusata), and dogwoods (C. disciflora). Seeds ofpines were consumed mostly during dry months(December 2000; January–May and September–December 2001). In June 2001, oaks startedproduction of mast and became the mostimportant food for squirrels during wet months

(June–September 2001). Production of mast byoak trees decreased gradually until December2001, and so did consumption by squirrels,which fed on seeds of whichever species of oakthat was producing mast at the time. Cornusdisciflora produced seeds during most of the yearand was an important food for squirrels. Previousreports indicated that Mexican red-bellied squir-rels in Michoacan fed on acorns and seeds ofpines according to the season (Nelson, 1899).The introduced population of Mexican red-bellied squirrels in Florida similarly varies itsdiet widely to feed upon whichever type of foodis abundant each season (Brown and McGuire,1975). Although caching food is common inother tree squirrels in temperate forests (Stapa-nian and Smith, 1984; Koprowski, 1991; Hurlyand Lourie, 1997), we only observed oneinstance of a squirrel caching a pine cone in abranch fork and concealing it with pine needles.Squirrels may rarely cache food due to snow-freewinters and abundance of food in our study area.

Squirrels were observed using leaf nests in thefollowing species of trees: Q. candicans, Q.crassipes, Q. laurina, Q. obtusata, P. pseudostrobus,C. mexicana, C. disciflora, and S. ramirezii. Squirrelsbuilt nests in forks of oak trees and in branchesof both oak and pine trees. Nests built inbranches of oak trees consisted only of aplatform of leafy branches interwoven in acircular shape like those described for other treesquirrels (Brown, 1984; Koprowski, 1994a,1994b). Nests built in branches of pine treeswere similar to those of Abert’s squirrels (Sciurusaberti), built close to the main trunk with twigsand pine needles interwoven in a circular shape(Farentinos, 1972; Brown, 1984). We observedsquirrels building leaf nests on four occasions:November and December 2000, and January andMarch 2001. In all events, squirrels built nests inforks of oak trees by biting off leafy branches 20–30 cm long from the same tree or a nearby oaktree. Squirrels interwove branches giving the nesta spherical shape. The individual observed inNovember 2000 started construction of its nest atca. 1000 h and completed it at ca. 1600 h. Whenfinished, the squirrel descended and collecteddry leaves from the forest floor to provision itsnest. The same procedure was used for nestsbuilt in forks of C. disciflora, C. mexicana, and S.ramirezii. On 16 January 2001, we found a leafnest on the ground made with leaves of S.ramirezii and dry leaves inside. A similar nest-

September 2011 Notes 401

building behavior has been described in theintroduced population of Mexican red-belliedsquirrels in Florida (Brown and McGuire, 1975)and in other tree squirrels (Brown, 1984;Setoguchi, 1991; Lurz et al., 2005).

Squirrels did not use nest boxes. It is possiblethat their reluctance to use nest boxes was due toa lack of natural tree cavities in the study area.Structure of the forest was characterized by treeswith basal diameters considerably smaller (mean5 17.3 cm 6 11.4 SD, n 5 90) compared to thoseof nest trees (mean 5 59.1 cm 6 30.1 SD, n 5 90;t 5 15.38, df 5 178, P , 0.001), which mightaccount for our failure to observe tree cavities. InFlorida, Mexican red-bellied squirrels use treecavities for nesting although availability of thesenatural structures was limited (Brown andMcGuire, 1975). Nest boxes may have neededto be placed higher or left longer so squirrelshad time to habituate to them.

As previously reported (Brown and McGuire,1975; Ceballos and Galindo, 1984), Mexican red-bellied squirrels showed year-round breedingactivity compared to the distinctly seasonalbreeding of tree squirrels in temperate forests;availability of food is believed to be the limitingfactor in their reproduction (Ceballos andGalindo, 1984). We observed males with scrotaltestes on 18 January 2001, lactating females on28 December 2000 and 15–19 January 2001,mating chases on 20–28 December 2000, 12March, 11 April, 17–18 July, 17 August, 16October, and 27 December 2001, and presenceof juveniles on 20 December 2000, 15–18January, 10 March, 16–18 June, 17 August, 27November, and 24 December 2001. The threeadult males collected for museum specimensweighed on average 591.7 g (652.0 SD) andpossessed scrotal testes. The two adult femalesweighed on average 562.5 g (617.7 SD); one waslactating and the other postlactating. The juve-nile male weighed 375 g and possessed smalltestes. On 29 December 2000 at 0830 h, weobserved three juveniles (two gray and onemelanistic) coming out of a leaf nest in a pinetree. All squirrels moved to nearby trees and fedon seeds of pines and oaks close to their nest.The species produces 2–4 young/litter (Ceballosand Galindo, 1984).

As in much of their range, including theintroduced population in Florida, Mexican red-bellied squirrels in our study area presentedmelanistic variation (Nelson, 1899; Musser, 1968;

Brown and McGuire, 1975; Ceballos and Ga-lindo, 1984). However, unlike the gray-red colorphase described in Florida (Brown and McGuire,1975), squirrels in our study area were gray withwhite underparts (Nelson, 1899; Musser, 1968),while melanistic animals were totally black. Wevisually estimated a color-phase ratio of ca. 70%gray squirrels and 30% melanistic.

Mexican red-bellied squirrels were more activein early morning and before sunset like otherspecies of tree squirrels (Brown, 1984; Koprowskiand Corse, 2005); we regularly observed themresting or sleeping on branches of oak and pinetrees around midday. During winter, squirrelswaited for ambient temperature to increasebefore beginning activities. Daily activities werenoticeably reduced during hot and sunny days orduring strong winds. Similar to the introducedpopulation in Florida (Brown and McGuire,1975), squirrels in our study area were shy,elusive, solitary, and retreated from the areathrough the forest canopy when intrudersapproached. Occasionally, squirrels showed ag-gressive behavior to an intruder emitting barkswhile moving the tail forward and backwardrapidly. Contrary to the population in Florida,where squirrels rarely came to the ground(Brown and McGuire, 1975), squirrels in ourstudy area were observed year-round exploringthe forest floor, especially during the dry season.We did not observe aggressive behavior towardconspecifics that might suggest territorial behav-ior. However, whether Mexican red-bellied squir-rels are territorial or not is unknown.

Sciurus aureogaster has been reported to dam-age cornfields planted in clearings in the forest(Nelson, 1899). In 2001, we were informed bylocal people that these squirrels fed in theirorchards and cornfields, suggesting that thesesquirrels are locally common. During our 5-days/month visits in 2001, we observed on average34.6 squirrels/visit (621.6 SD; range 5 12–69;0.4 squirrel/ha). However, because of theirelusive behavior, and their movements betweenpatches of forest (Nelson, 1899), it was difficultto effectively assess size of the population.

Because most of our knowledge about treesquirrels comes from temperate latitudes (Ko-prowski and Nandini, 2008), it is unknownwhether measures used in temperate forests topreserve and manage arboreal squirrels would beeffective in tropical latitudes. As a result, it isimportant to generate more information on the

402 The Southwestern Naturalist vol. 56, no. 3

ecology of arboreal squirrels in tropical forests,which are the centers of diversity and endemismof tree and flying squirrels (Sciurus and Glauc-omys; Koprowski and Nandini, 2008).

We thank J. Lemos and G. Ceballos for valuablecomments during the study. The Herbario NacionalMEXU and S. Valencia from the Facultad de Cienciasof the Universidad Nacional Autonoma de Mexicohelped with identification of trees. The ServicioMeteorologico Nacional provided data for temperatureand precipitation for 2001. Municipal authorities ofPatzcuaro, Michoacan, provided the permit to installnest boxes. The Consejo Nacional de Ciencia yTecnologıa and the Direccion General de Estudios dePosgrado of the Universidad Nacional Autonoma deMexico awarded scholarships to NR-L. J. L. Koprowskiand one anonymous reviewer provided valuable com-ments that improved the manuscript.

LITERATURE CITED

BARKALOW, F. S., AND R. F. SOOTS. 1965. An improvedgray squirrel nest box for ecological and manage-ment studies. Journal of Wildlife Management 29:679–684.

BROWN, D. E. 1984. Arizona’s tree squirrels. ArizonaGame and Fish Department, Phoenix.

BROWN, L. N., AND R. J. MCGUIRE. 1975. Field ecology ofthe exotic Mexican red-bellied squirrel in Florida.Journal of Mammalogy 56:405–419.

CEBALLOS, G., AND C. GALINDO. 1984. Mamıferos silvestresde la cuenca de Mexico. Ed. Limusa-Instituto deEcologıa, Universidad Nacional Autonoma deMexico, Mexico, Distrito Federal, Mexico.

FARENTINOS, R. C. 1972. Nests of the tassel-earedsquirrel. Journal of Mammalogy 53:900–903.

HURLY, T. A., AND S. A. LOURIE. 1997. Scatterhoardingand larderhoarding by red squirrels: size, disper-sion, and allocation of hoards. Journal of Mammal-ogy 78:529–537.

KOPROWSKI, J. L. 1991. Response of fox squirrels andgray squirrels to a late spring-early summer foodshortage. Journal of Mammalogy 72:367–372.

KOPROWSKI, J. L. 1994a. Sciurus niger. MammalianSpecies 479:1–9.

KOPROWSKI, J. L. 1994b. Sciurus carolinensis. MammalianSpecies 480:1–9.

KOPROWSKI, J. L., AND M. C. CORSE. 2005. Time budgets,activity periods, and behavior of Mexican foxsquirrels. Journal of Mammalogy 86:947–952.

KOPROWSKI, J. L., AND R. NANDINI. 2008. Global hotspotsand knowledge gaps for tree and flying squirrels.Current Science 95:851–856.

LURZ, P. W. W., J. GURNELL, AND L. MAGRIS. 2005. Sciurusvulgaris. Mammalian Species 769:1–10.

MCGUIRE, R. J., AND L. N. BROWN. 1973. Coconut feedingbehavior of the red-bellied squirrel on Elliot Key,Dade County, Florida. American Midland Naturalist89:498.

MUSSER, G. G. 1968. A systematic study of the Mexicanand Guatemalan gray squirrel, Sciurus aureogaster, F.Cuvier (Rodentia: Sciuridae). Miscellaneous Publi-cations of the Museum of Zoology, University ofMichigan 137:1–112.

NELSON, E. W. 1899. Revision of the squirrels of Mexicoand Central America. Proceedings of the Washing-ton Academy of Sciences 1:15–110.

RAMOS-LARA, N., AND F. A. CERVANTES. 2007. Nest-siteselection by the Mexican red-bellied squirrel(Sciurus aureogaster) in Michoacan, Mexico. Journalof Mammalogy 88:495–501.

SECRETARIA DE MEDIO AMBIENTE Y RECURSOS NATURALES.2002. Norma Oficial Mexicana NOM-059-ECOL-2001, proteccion ambiental-especies nativas deMexico de flora y fauna silvestres-categorıas deriesgo y especificaciones para su inclusion, exclu-sion o cambio-lista de especies en riesgo. DiarioOficial de la Federacion, 6 de marzo del 2002:1–56.

SETOGUCHI, M. 1991. Nest-site selection and nest-building behavior of red-bellied tree squirrels onTomogashima Island, Japan. Journal of Mammalo-gy 72:163–170.

STAPANIAN, M. A., AND C. C. SMITH. 1984. Density-dependent survival of scatterhoarded nuts: anexperimental approach. Ecology 65:1387–1396.

THORINGTON, R. W. JR., AND R. S. HOFFMANN. 2005. FamilySciuridae. Pages 754–818 in Mammal species of theWorld: a taxonomic and geographic reference (D.E. Wilson and D. M. Reeder, editors). Thirdedition. John Hopkins University Press, Baltimore,Maryland.

Submitted 24 June 2009. Accepted 13 January 2011.Associate Editor was Richard T. Stevens.

September 2011 Notes 403