My research interests are in the behavioral, physiological, and biochemical adaptations of mammals to extreme environments.  I am particularly interested in how these adaptations integrate to prepare mammals for thermal stress.  My laboratory is presently focusing on three areas of research: 1) hibernation, 2) food storage, and 3) the combined use of both hibernation and food storage as an over-winter strategy.  My laboratory is also investigating how recent climate change is affecting the evolution of these strategies.

• The evolutionary physiology of hibernation: Ground squirrels (Spermophilus spp.) are herbivorous rodents that hibernate for periods of up to 8 months.  Stored body fats (triacylglycerols) are the sole source of energy utilized during hibernation.  The goal of my research in this area is to determine the ecological factors that favored the evolution of hibernation as an over-winter survival strategy for these rodents.  The physiological/biochemical basis of mammalian hibernation is unknown.  My past research with Spermophilus lateralis, however, revealed that moderately high amounts of polyunsaturated fatty acids (PUFAs) are required in the diet during the summer fattening period for hibernation to occur properly in the fall.  PUFAs cannot be synthesized by mammals, but most plant tissues commonly produce them.  Additional studies with S. lateralis revealed that hibernation is best when the dietary linoleic acid content is between 33 and 74 mg/g.  I have also demonstrated that S. lateralis has a dietary preference for food items within this range of PUFA contents, and this level of PUFA intake is maintained by free-ranging ground squirrels through their diet selection.

• The evolution of food storage: Red squirrels (Tamiasciurus hudsonicus) do not hibernate, they instead survive winter by feeding on conifer seeds and fungal sporocarps (mushrooms and truffles) stored during the previous summer.  The ecological factors that favored the evolution of food hoarding rather than hibernation by this species are poorly understood.  The goal of my research with red squirrels is to determine the ecological/evolutionary limitations of food hoarding.  Four of the five conifer seed species stored by T. hudsonicus in Pinaleño Mountains of Arizona greatly decrease in nutritional quality during winter storage.  My research demonstrated that the development of complicated food hoarding preferences and stored seed management strategies are required for natural selection to favor seed hoarding.  Red squirrels also air dry fungal sporocarps (mushrooms) in the branches of trees before storing them.  This strategy preserves their nutritional quality as long as air temperatures remain below 0^o C during storage.
  
  The effects of climate change on hibernation: Winter air temperatures have increased in the Northeast during the past 100 years, and will increase 4^o C further within 70 years.  One group of mammals that may be particularly sensitive to climate change is those that hibernate during winter since body temperatures during torpor are influence by ambient temperature.  Eastern chipmunks (Tamias striatus) store seeds in underground burrows for winter consumption, and they reduce their rate of energy utilization with long torpor bouts.  My laboratory has been conducting a long-term study on the relationship between ambient (air/soil) temperature and the torpor patterns of free-ranging T. striatus in Southeastern New York State using temperature sensitive radio-collars from November 2000 to present.
  
  

2007 - present: Editorial Board Member, Physiological and Biochemical Zoology
2004 - 2007: Associate Editor, Journal of Mammalogy
2007 - Certificate of Recognition, American Society of Mammalogists
2007 - Certificate of Recognition, Fordham University CSTEP

Frank, C.L., S. Karpovich, and B.M. Barnes (2007). The relationship between natural variations in dietary fatty acid composition and the torpor patterns of a free-ranging arctic hibernator.  Physiological and Biochemical Zoology, (in press).

Frank, C.L. (2006).  The nutritional ecology of fungal sporocarp consumption and hoarding by the Mount Graham red squirrel. In: Sanderson, HR, Koprowski, JL. (eds). Ecology of Endangerment:  The Mt. Graham Red Squirrel and its Last Refuge, University of Arizona Press. (in press).

Frank, C.L., and S. Cox (2006).  The adaptive significance of seed hoarding by the Mount Graham red squirrel. In: Sanderson, HR, Koprowski, JL. (eds). Ecology of Endangerment:  The Mt. Graham Red Squirrel and its Last Refuge, University of Arizona Press. (in press).

Frank, C.L., W.R. Hood, and M.C. Donnelly (2004). The role of x-Linolenic acid (18:3) in mammalian torpor.  Pages 71-90.  In: Life in the Cold: Evolution, Mechanisms, Adaptation and Application. Edited by B.M. Barnes and H.V. Carey. Institute of Arctic Biology Press.

Frank, C.L. (2002). The effects of short-term variations in diet fatty acid composition on  mammalian torpor.  Journal of Mammalogy, 83(4): 1013-1019.

Harlow, H.J., and C.L. Frank (2001).  The role of dietary fatty acids in the evolution of spontaneous and facultative hibernation patterns in prairie dogs.  Journal of Comparative Physiology B., 171: 77-84.

Frank, C.L., A. Gibbs, E.S. Dierenfeld , and J.V. Kramer (2000).  The effects a-tocopherol on mammalian torpor.  Pages 207 - 213 In: Life in the Cold.  Edited by G. Heldmaier and M. Klingenspor.  Springer-Verlag, New York.

Carey, H.V., C.L. Frank, and, J. Seifert (2000).  Hibernation induces oxidative stress and activation of NFkB in ground squirrel intestine.  Journal of Comparative Physiology B.,170: 551 - 559.

Carey, H.V., C.L. Frank, and T.Y. Aw (2000).  Cellular responses to metabolic stress in hibernating mammals.  Pages 339 - 346 In: Life in the Cold.  Edited by G. Heldmaier and M. Klingenspor.  Springer-Verlag, New York.

Frank, Craig L., Ellen S. Dierenfeld, and Kenneth B. Storey (1998). The relationship between lipid peroxidation, hibernation, and food selection in mammals. American Zoologist, 38(2):341-349.

Frank, Craig L., Stephen P. J. Brooks, Henry J. Harlow, and Kenneth B. Storey (1998). The influence of hibernation patterns on the critical enzymes of lipogenesis and lipolysis in prairie dogs. Experimental Biology Online, 3:90-99

Frank, Craig L., and Kenneth B. Storey (1996). The effect of total unsaturate content on hibernation. Pages 211-216 in: Adaptations to the Cold. Edited by F. Geiser, T. Hulbert, and S. Nicol. University of New England Press, Armidale, Australia.

Frank, Craig L., and Kenneth B. Storey (1995). The optimal depot fat composition for hibernation by golden-mantled ground squirrels (Spermophilus lateralis). Journal of Comparative Physiology B, 164(7):536-542.

Frank, Craig L. (1994). Polyunsaturate content and diet selection by ground squirrels (Spermophilus lateralis). Ecology, 75(2):458-463.

Frank, Craig L. (1992). The influence of dietary fatty acids on hibernation by golden-mantled ground squirrels (Spermophilus lateralis). Physiological Zoology, 65(5):906-920.

Frank, Craig L. (1991). Adaptations for hibernation in the depot fats of a ground squirrel (Spermophilus beldingi). Canadian Journal of Zoology, 69:2707-2711.

Frank, Craig L. (1988). Diet selection by a heteromyid rodent: role of net metabolic water production. Ecology, 69(6):1943-1951.

Frank, Craig L. (1988). The relationship of water content, seed selection, and the water requirements of a heteromyid rodent. Physiological Zoology, 61(6):527-534.

Frank, Craig L. (1988). The influence of moisture content on seed selection by kangaroo rats. Journal of Mammalogy, 69(2):353-357.

Frank, Craig L. (1988). The effects of moldiness level on seed selection by Dipodomys spectabilis. Journal of Mammalogy, 69(2):358-362.