Evaporative Water Loss in Desert Rodents in Their Natural Habitat

A glass housing unit for the study of rodent burrowing behavior is described. The results of 18 months of burrowing for a family of Meriones unguiculatus are depicted. The system can be used to investigate relationships among the animals' behaviors, communication processes, and ecology.The most widely studied rodents in the behavioral laboratory, the rat (Rattus norvegicus), mouse (Mus musculus), gerbil (Meriones unguiculatus}, and hamster (Mesocricetus auratus) are investigated almost entirely in isolation from their normal habitat. Paradoxically, they are then required to demonstrate behaviors we believe to be part of their species-typical repertoire (Lockard, 1968). While we can gain considerable information in this fashion, and certainly control the relevant stimuli, in the end we lack certainty as to the ecological importance of the behaviors we so assiduously measure. The message is not to abandon the typical laboratory approach, of course, but to pay more attention to the normal ecology of our fossorial and semifossorial species.To this end we have devised a large glass-enclosed, dirt-filled living area for the study of rodent behavior. The living area is described here, along with the burrow system constructed by a family of Mongolian gerbils, Meriones unguiculatus. The advantages of studying behavior in this context are discussed. Other seminatural observation areas have been described for the Norway rat (Boice, 1977;Flannelly & Lore, 1977) and the Mongolian gerbil (Agren, 1976;Roper & Polioudakis, 1977). LIVING AREA: GERBILCITYThe living enclosure is constructed from double-pane window glass in the shape of a square-cornered horseshoe. It rests on a sheet-metal floor and is open at the top. The glass panes are rigidly joined with aluminum struts. The exact dimensions are seen in Figure 1. Its size requires a room approximately 3.7 x 5.5 m, allowing the investigator to view the burrows from all sides and from within the central opening of the horseshoe. Sandy loam fills the area to the depth of 60 em.This work was sponsored by NIMH Grant MH 14076-13, awarded to Del D. Thiessen. Our thanks to Capital GlassCompany of Austin for a particularly fine job of construction. Our thanks, too, to the gerbils who provided us with so much information and hours of entertainment. BURROW SYSTEMThe nature of the gerbil burrow system was observed following the introduction of four pairs of adults. All were socially naive and had been living for several weeks in isolated cages. Ad-lib water was provided in a pie plate at one comer of the area, and fist-sized rocks and small logs were placed over the surface. Purina Lab Chow pellets were tossed into the area several times a week.Within 1 week of the introduction of the gerbils, a dominant male and female pair emerged. The dominant pair dug tunnels, hoarded food, and prevented the remaining gerbils from establishing burrows. Within 3 weeks, the subordinate animals were killed by attacks or starved to death. The dominant pair eventually gave birth to two litters of four pups...

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“…1l)74~Chapman & Bennett. 1975: Daly & Daly, 1975;Kenagy, 1976;Lore & Flannelly, 1978;B. Schmidt-Nielsen & K. Schmidt-Nielsen, 1950;K.…”

Section: Discussionunclassified

A glass rodent enclosure: Gerbil City

Thiessen

Maxwell

1979

Behavior Research Methods & Instrumentation

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“…Kangaroo rats, specifically Dipodomys merriami, were one of the first desert animals to be extensively and systematically studied. The overall conclusion or assumption of these studies was that these animals are able to occupy desert conditions on a diet of dry seeds without drinking (Schmidt-Nielsen and Schmidt-Nielsen 1950, 1951, 1952Schmidt-Nielsen 1964;MacMillen 1964MacMillen , 1972MacMillen and Hinds 1983;Hulbert and MacMillen 1988). This ability, which was attributed to a combination of physiological mechanisms for conserving water and behavioral avoidance of extreme conditions, has strongly influenced our general view of desert mammals.…”

Section: Concluding Comments and Broader Significancementioning

confidence: 99%

“…The traditional views of kangaroo rat microclimate selection embrace three aspects: kangaroo rats avoid high temperatures by restricting surface activity to nighttime hours when environmental temperatures are at their minimum (Schmidt-Nielsen and Schmidt-Nielsen 1950;French 1993;Degen 1997), burrow temperatures are cool (e.g., <25°C), and occupancy of a burrow suppresses evaporative water loss due to its higher ambient humidity (Schmidt-Nielsen and Schmidt-Nielsen 1950;French 1993;Degen 1997). These views have been propagated in popular ecology textbooks as well (see Pough et al 1996).…”

Section: Introductionmentioning

confidence: 99%

“…These views have been propagated in popular ecology textbooks as well (see Pough et al 1996). However, often-cited studies measuring temperature (e.g., Vorhies 1945) and humidity (Schmidt-Nielsen and Schmidt-Nielsen 1950) of burrows of this and other desert rodents were conducted in comparatively mesic areas or after heavy rainfall and may not reflect the typical conditions of the Sonoran Desert (Walsberg 2000). Also correlated with this portrayal of survival in desert conditions by emphasis on conservation of water and behavioral avoidance of extreme conditions is the view that kangaroo rats are intolerant of high environmental temperatures (Carpenter 1966;Yousef and Dill 1971).…”

Section: Introductionmentioning

confidence: 99%

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Kangaroo rats revisited: re-evaluating a classic case of desert survival

Tracy

Walsberg

2002

Oecologia

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Kangaroo rats are the archetypical organisms for mammalian survival in North American deserts, yet there are contradictions in the data surrounding their physiology and ecology. The traditional view has been that these nocturnal rodents have little tolerance to high temperatures (e.g., >30°C), reside in cool, humid burrows to escape the heat of the day, and nearly exclusively rely on a dry, carbohydrate-rich diet from which they metabolically derive most of their water supply. To test this view, we measured the microclimates, activity, and diet of Merriam's kangaroo rats (Dipodomys merriami) from a xeric location within the center of the Sonoran Desert. We arrive at the following conclusions: 1. Burrows are much hotter during the summer than previously appreciated. For over 100 days of the year, soil temperatures exceed 30°C at depths to 2 m. For over 50 days, temperatures exceed 35°C at depths to 1.5 m. These high temperatures at such depths preclude kangaroo rats from locating to cool temperatures (e.g., <30°C) by burrowing. 2. Kangaroo rats remain in shallow burrows (<1 m) at relatively high ambient temperatures (>35°C) throughout the daytime during the summer instead of residing deep within the soil. This finding supports recent laboratory experiments that show kangaroo rats have much higher thermal tolerances than previously realized. 3. Kangaroo rats do not restrict their activity to the coolest periods of the night, but are active immediately following sundown, during the hottest time of the night. 4. Burrows are not persistently humid, but can be quite dry. 5. Insects and succulent vegetation constitute a significant portion of a kangaroo rat's diet and may be key to their survival in the hot desert environment.

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“…decreases the effectiveness of evaporation for heat loss and water is thereby conserved (Schmidt-Nielsen and Schmidt-Nielsen 1950, Baudinette 1972, Gettinger 1975. Other avenues for heat loss, e.g.…”

Section: Vapour Pressurementioning

confidence: 99%

Refuge microclimates of rodents: a surface nesting Otomys unisulcatus and a burrowing Parotomys brantsii

Plessis¹,

Kerley²,

Winter³

1992

Acta Theriol.

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We investigated microclimates of the nest of Otomys unisulcatus Cuvier, 1829 and the warren of Parotomys brantsii (Smith, 1834) during two seasons and correlated these with the rodents' physiology. In both rodents' refuges, temperature varied less than ambient temperature (TA). In winter, temperatures in the O. unisulcatus nest at 40 cm below the nest apex, and in the P. brantsii warren 15 cm below the soil surface, were higher than nocturnal TA. In summer, during the hours of highest TA, refuges were cooler than TA. Vapour pressure (v.p.) in the refuges varied less and was higher than ambient v.p. In the humid refuges, heat loss by conduction rather than evaporative water loss is suggested. The nest of O. unisulcatus, with less temperature variation in winter and lower temperatures in summer, was less dependent of TA than P. brantsii's warren. The use of these refuges therefore contributes to the survival of these mesic rodents in a semi-arid region.

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Evaporative Water Loss in Desert Rodents in Their Natural Habitat

Cited by 100 publications

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A glass rodent enclosure: Gerbil City

A glass rodent enclosure: Gerbil City

Kangaroo rats revisited: re-evaluating a classic case of desert survival

Refuge microclimates of rodents: a surface nesting Otomys unisulcatus and a burrowing Parotomys brantsii

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