Grasshopper mouse

Abstract: Various aspects of reproductive behavior and of both maternal and paternal behavior are described for Onychomys torridus longicaudus. Data are presented on early development of young and are utilized as a background for indicating the age at which mice can enter the population as reproductive contributors. Although laboratory-raised females tend to be slow in attaining sexual maturity, O. t. longicaudus gains reproductive status in the field at an age comparable to that of some of its more prolific peromyscan relatives.

Abstract: The audiograms of two wood rats and three grasshopper mice were determined with a conditioned avoidance procedure. The wood rats were able to hear tones from 940 Hz to 56 kHz at a level of 60 dB (SPL), with their best sensitivity of -3 dB occurring at 8 kHz. The hearing of the grasshopper mice ranged from 1.85 kHz to 69 kHz at 60 dB (SPL), with their best sensitivity of 9 dB also occurring at 8 kHz. These results support the relation between interaural distance and high-frequency hearing and between high- and low-frequency hearing. The inability of the grasshopper mouse to hear low frequencies as well as other desert rodents such as kangaroo rats and gerbils demonstrates that not all rodents found in deserts have developed good low-frequency hearing. The degree to which general and specific selective pressures have played a role in the evolution of rodent hearing is discussed. A comparison of the hearing abilities of rodents reveals wide variation in the ability of different species to hear high- and lowfrequency sounds. Of the seven species whose hearing is known, high-frequency hearing ranges from an upper limit of 33 kHz in the chinchilla to 92 kHz in the wild house mouse. Low-frequency hearing also varies over a wide range, with the kangaroo rat hearing as low as 42 Hz while the comparable limit for the house mouse is 2.3 kHz (for a review, see H. Heffner & Masterton, 1980). Thus, rodents show much of the same diversity in hearing that has been shown to exist among mammals as a whole (cf. R. Heffner & Heffner, 1982, 1983). For the most part, the variation in rodent hearing can be accounted for by the same general factors that have been used to explain the variation in mammalian hearing. Specifically, animals with small functional interaural distances (i.e., small heads and

Abstract: The role of the vibrissae in cricket predation was examined in northern grasshopper mice (Onychomys leucogaster). Vibrissal amputation greatly increased kill latencies but had no effect on latency to initiate pursuit or on killing and consummatory behavior. The increased kill latencies resulted from repeated failures to pin the cricket with the forepaws and seemed to reflect disrupted timing of pouncing when the cricket was within 1-3 cm of the mouse. Vibrissal stimulation differs from audition, vision, and olfaction in its contribution to the integration of grasshopper mouse predatory behavior.