conservation.arizona.edu - Mearn’s squirrel

Ramos-Lara, N., and J.L. Koprowski. 2012. Communal nesting behavior in Mearns’s squirrels (Tamiasciurus mearnsi). Southwestern Naturalist 57: 195-225.

thackerk1 — Tue, 30 Jul 2019 18:18:57 +0000

Authors

Nicolás Ramos-Lara

John L. Koprowski

Communal nesting has been observed frequently in arboreal squirrels of the genus Sciurus and Glaucomys, but only occasionally in Tamiasciurus. During 2006 and 2007, we trapped and radiocollared 38 adult Mearns’s squirrels (Tamiasciurus mearnsi) in Baja California, Mexico, to examine their nesting behavior. We report for the first time instances of communal nesting in Mearns’s squirrels. Same-sex groups were more common than mixed-sex groups. Females engaged more in communal nesting than males. Communal nesting behavior in Mearns’s squirrels seems to be similar to other species of arboreal squirrels; decreasing as mean monthly temperature increases and during the breeding season.

Additional Information

COMMUNAL NESTING BEHAVIOR IN MEARNS’S SQUIRRELS (TAMIASCIURUS MEARNSI)

Date of publication:

2012

Topics

arboreal squirrels

Mearn’s squirrel

communal nesting

nesting behavior

Ramos-Lara, N., J. L. Koprowski, and D. E. Swann. 2013. Nest-site characteristics of the montane endemic Mearns's squirrel (Tamiasciurus mearnsi): an obligate cavity-nester? Journal of Mammalogy 94:50-58.

thackerk1 — Tue, 30 Jul 2019 18:09:11 +0000

Authors

Nicolás Ramos-Lara

John L. Koprowski

Don E. Swann

Many animals depend on nests for their survival and reproduction, with some species considered obligate tree cavity-nesters. Mearns’s squirrel (Tamiasciurus mearnsi) is a species endemic to the Sierra de San Pedro Mártir, Baja California, Mexico, that relies on tree cavities for nesting. Federally listed as threatened in Mexico, and as endangered by the International Union for Conservation of Nature, the ecology of this southernmost Tamiasciurus is poorly known. The aim of this study was to examine the nesting requirements of Mearns’s squirrels. We used telemetry to locate the nests and 10-m-radius circular plots to compare habitat characteristics between nest sites and random sites, nest sites of males and females, and nest sites of breeding and nonbreeding females. Nest tree species, nest tree condition, nest tree size (diameter at breast height), canopy cover, and occurrence of white firs (Abies concolor) are important characteristics for nesting. Nest sites of males did not differ from those of females except for nest tree condition. Females apparently do not have specific nesting requirements for rearing young. Unlike other congeners that also build leaf nests and underground burrows for nesting, large trees and snags that facilitate cavity formation are critical for the conservation of this species.

Additional Information

Nest-site characteristics of the montane endemic Mearns’s squirrel (Tamiasciurus mearnsi): an obligate cavity-nester?

Date of publication:

2013

Topics

cavity nests

endemic species

nest sites

tree cavities

Mearn’s squirrel

Ramos-Lara, N., and J. L. Koprowski. 2015. Spacing behavior of a non-larder-hoarding Tamiasciurus: a study of Mearns's squirrels in xeric coniferous forests. Ethology 121: 196-205.

thackerk1 — Tue, 30 Jul 2019 17:43:48 +0000

Authors

Nicolás Ramos-Lara

John L. Koprowski

In ecosystems with seasonal fluctuations in food supply many species use two strategies to store food: larder hoarding and scatter hoarding. However, because species at different geographic locations may experience distinct environmental conditions, differences in hoarding behavior may occur. Tree squirrels in the genus Tamiasciurus display variation in hoarding behavior. Whereas red (Tamiasciurus hudsonicus) and Douglas’s (Tamiasciurus douglasii) squirrels in mesic coniferous forests defend territories centered around larder hoards maintaining non-overlapping home ranges, red squirrels in deciduous forests defend small scatter-hoarded caches of cones maintaining overlapping home ranges. As in other rodent species, variation in hoarding behavior appears to influence the spacing behavior of red and Douglas’s squirrels. In contrast, Mearns’s squirrels (Tamiasciurus mearnsi) in xeric coniferous forests neither rely on larder hoards nor appear to display territorial behavior. Unfortunately, little is known about the ecology of this southernmost Tamiasciurus. Using radiotelemetry, we estimated home-range size, overlap, and maximum distance traveled from nest to examine the spacing behavior of Mearns’s squirrels. Similar to scatter-hoarding rodents, maximum distance traveled from nest was greater for males during mating season, whereas those of females were similar year round. Although no seasonal differences were detected, male home ranges were three times larger during mating season, whereas those of females were smaller and displayed a minor variation between seasons. Home ranges were overlapped year round but contrary to our expectations, overlap was greater during mating season for both sexes, with no detectable relationship between male home-range size and the number of females overlapped during mating season. Overall, the results appear to support our hypothesis that in the absence of larder hoards, the spacing behavior of Mearns’s squirrels should be different from larder- hoarding congeners and more similar to scatter-hoarding rodents.

Additional Information

Spacing Behavior of a Non-Larder-Hoarding Tamiasciurus: A Study of Mearns’s Squirrels in Xeric Coniferous Forests

Date of publication:

2014

Topics

hoarding behavior

mating system

spacing behavior

tree squirrel

Mearn’s squirrel

red squirrel

Douglas's squirrel

Koprowski, J. L., N. Ramos, B. S. Pasch, and C. A. Zugmeyer. 2006. Observations on the ecology of the endemic Mearns's squirrel (Tamiasciurus mearnsi). The Southwestern Naturalist 51(3): 426-430.

thackerk1 — Mon, 22 Jul 2019 23:06:13 +0000

Authors

John L. Koprowski

Nicolás Ramos

Bret S. Pasch

Claire A. Zugmeyer

Mearns’s squirrel (Tamiasciurus mearnsi) is an endemic species of the montane forest of the Sierra de San Pedro Mártir in Baja California. Despite having been described for the first time in 1893 and a listing as threatened by Mexican authorities, no information is available on the ecology of this southernmost Tamiasciurus. We observed the ecology of Mearns’s squirrels during 2004 and 2005. Mearns’s squirrel apparently does not form larderhoards, known as middens, or leaf nests commonly built by other members of this genus. We observed Mearns’s squirrels to feed heavily on tree seeds and fungi. We noted males with scrotal testes and a female in estrus in late spring. We did not observe eastern gray squirrels (Sciurus carolinensis), introduced to the western Sierra in 1946, within the areas that we searched for T. mearnsi. Mearns’s squirrels might possess unique adaptations for their persistence in the dry, open forest of the Sierra de San Pedro Mártir.

Additional Information

OBSERVATIONS ON THE ECOLOGY OF THE ENDEMIC MEARNS’S SQUIRREL (TAMIASCIURUS MEARNSI)

Date of publication:

2006

Topics

Mearn’s squirrel

endemic species

adaptations

montane forest

Sierra de San Pedro Mártir

Tamiasciurus mearnsi (Rodentia: Sciuridae)

thackerk1 — Mon, 22 Jul 2019 21:30:50 +0000

Authors

John L. Koprowski

Michael A. Steele

Nicolás Ramos-Lara

Tamiasciurus mearnsi (Townsend, 1897) is a small-sized tree squirrel commonly called Mearns’s squirrel. One of 3 species that comprise the genus Tamiasciurus, T. mearnsi, is endemic to the Sierra de San Pedro Mártir in Baja California, Mexico; it is considered rare and occurs only at low densities. T. mearnsi is federally listed as “Threatened” in Mexico and is also included in the International Union for the Conservation of Nature and Natural Resources Red List of Threatened Species as “Endangered.” The introduction of the eastern gray squirrel (Sciurus carolinensis) may be a serious threat to this relict species.

Additional Information

Mammalian Species 48:66-72

Date of publication:

2016

Topics

Mearn’s squirrel

tree squirrel

endemic species

eastern gray squirrel

Sierra de San Pedro Mártir

Mexico

Research Categories

Natural History Threatened and Endangered Species