1997-06-13_REPORT - M1981302 ‎(18)‎

• Permit No: M1981302
• IBM Index Class Name: Report
• Doc Date: 6/13/1997
• Doc Name: EXHIBIT A STATUS REPORT ON ZAPUS HUDSONIUS PREBLEI A CANDIDATE ENDANGERED SUBSPECIES
• Media Type: D
• Archive: No

C. Interspecirrc- Z. hudsonius are docile creatures, but there is some evidence that
they will defend themselves when attacked (Quimby 1951). A subadult
imprisoned with an adult meadow mouse, Microtus pennsylvanicus, was killed
and badly mutilated during a struggle. The much larger meadow mouse, although
not mortally wounded, suffered a severe gash in the upper lip, evidently inflicted
by the incisors of the jumping mouse. Whitaker (1972) reported that in habitats
where there appeared to be sufficient food, other species of mammals, if they did
compete, did not limit the distribution or abundance of Zapus. As mentioned
above under Jumping, when frightened Z. hudsonius escapes by means of long
bounds, and then stops, may progress by crawling low to the ground, and may
remain motionless, at times with its white ventral region pressed close to the
ground, using its coloration as camouflage (Quimby 1951).
11. Physiology
A. Thermoregulation-The average body temperature of Z.hudsonius was calculated
to be 37.27°C (range 35.1 to 40.1°C),but expresses a rhythmic daily cycle,being
highest at night (mean of 38.0°C) and lowest during the day (mean of 36.9°C)
(Whitaker 1972). This daily fluctuation reflects the nocturnal behavior pattern of
this species. During exposure to temperatures of 0 to 10°C, the body temperature
of a Z. hudsonius was unstable. In response to ambient night temperatures less
than zero, the body temperature increased to a normal nighttime active
temperature of about 38°C, and was apparently the result of increased metabolic
activity. This activity was interpreted to be beneficial in keeping the animal from
freezing, and was similar to activity found in other hibernating mammals
(Whitaker 1972). During dormancy, rectal temperatures were found to be at least
YC higher than ambient temperatures above 0°C. In response to ambient
temperature below 0°C, skin temperature rose from 3 to 10°C. The body
temperature of one animal during emergence from hibernation rose from 2 to
25°C in 30 minutes, fluctuated between 25 and 33°C for about an hour, and
• leveled off at 330C thereafter (Whitaker 1972).
B. Oxygen consumption- Whitaker (1972) presented information on oxygen
consumption of a Z. hudsonius as it entered hibernation. At an ambient
temperature of 29°C, oxygen consumption was about 2000 mm3/tu1g of body
weight. At 10°C, oxygen consumption rose to between 5000 and 60()0 mm3.
Metabolic response dropped slightly in the first hour, dropped to 200 ram' the
next half hour, and reached a minimum of 40 mm' in another 4 hours. After
waking spontaneously, the animal utilized 5000 ram' necessary for maintenance
at 10°C within an hour of emergence.
C. Weight fluctuation- Z. hudsonius puts on fat, deposited in a thin layer over the
inside of the skin, over the back, and in body cavities, in the aurumn in
preparation for hibernation (Krutzsch 1954). Weight gain can be rapid and
extensive. One individual fattened from 19 to 37 g, with average daily increases
of 1.9 to 2.0 g per day. A 6 to 8% increase in body weight per day was observed
in some individuals over three days. The rate was found to be lower over longer
periods, with periods of increase interspersed with periods of non-increase.
Increase in weight is not synchronized among individuals. Jumping mice that
fatten on short days before hibernation hibernated for longer periods than mice
that fattened on long days (Whitaker 1972).
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