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Edie, the first Least Weasel: 7/30/2013, 24g (arrived 7/29 @ 21 g), 4‐5 wks old
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Research has centered on three major areas of study: (a) physiology of delayed implantation; (b) physiology of coat color changes; and (c) economic importance as fur bearers. Color changes may not occur in the southern part of the range, and there appears to be a genetic component. A southern animal taken north will not change color; a northern one taken south will continue to change.
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Least Weasels, 2 juv – 6‐7 wks old: 11/18/14, 25.2 & 29g; 11/19: 31.6 & 37.9 g
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Short‐tailed Weasel: 6/12/2015, 35 g; was 17 g on 6/6/15 @ 4 wks
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Long Tailed Weasel: 5/3/2015, 20 g – 2.5 (3?) wks old; 5/9/2015, 32.6 g
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They are remarkable for their length and slenderness. As a comparison, the length of a raccoon spine = length of the hind leg; for weasels the spine = 1.75x hind leg.
Weasels expend a lot of energy keeping warm. Their fur is not particularly well insulation, and their shape prevents them from curling into a tight ball, conserving energy.
Delayed implantation: Most are northern animals, high in the ecological food chain, and not a rapid turnover (i.e., short life expectancy) so no need for multiple litters in a year. Mating in spring/summer is beneficial to the adults while an early spring birth benefits the young (longer time to grow up before winter sets in). There is evidence that at least sometimes the male is around to help raise the young because the female goes into estrus soon after giving birth. It also serves as a means of population control for such an efficient predator. In the case of Least Weasels the need to have more offspring out trumps the climate pressure for delay due to the shorter life expectancy.
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Long‐tailed weasel.
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Long‐tailed weasel. He would burrow up through the fleece, then stick his head out and fall asleep.
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MER is RESTING; Average Daily Metabolic Rate (ADMR) of least weasels determined to be about 2x MER. LW: female ave 0.33 g/g/d increasing to 0.75 g/g/d during lactation for a litter of four (East and Lockie).
Need to eat frequent (every 2‐3 hours) small (few gram) meals. They cannot gorge or eat more often even if under fed. Many die of starvation, especially in traps or when mice populations crash.
Lactating female ate > 70% BW/day
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Raising a family of 6 long‐tailed weasels
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Note the birth weight difference between the weasels and the mink. Like many other mammals, the eyes often open over a period of several days.
In the wild LW and LTW co‐exist more peacefully than LW and STW, possibly because they do not compete for the same prey. The LW preys on smaller mice in areas inaccessible to LTW.
In rehab, do not combine with other species (applies to all mustelids; skunks are the one possible exception).
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STW raised on FV Kitten (40/25) : Ultraboost (25/54) : Water, 3:1:8. LW and LTW raised on opossum, 25/30
The female does not leave during the first four days after giving birth; sometimes a male is around to help.
Feed only if hungry and suckling vigorously. Weak kits may be hypothermic, dehydrated, and/or hypoglycemic. Prone to hypoglycemia. If found cool to the touch or cold first warm then administer some dextrose (2.5% or 5%) or corn syrup and fluids as necessary. Somewhat inconsistent appetite is normal.
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LTW. Baby vampire teeth. 5/10/15; 37.2 g
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STW, 6/9/2015 26.4 g
The young mustelids are called “kits.” And sometimes “cubs” (depending on which source you are consulting). 
At birth the front limbs are much stronger and better coordinated than the rear limbs. Newborns are surprisingly strong, lifting their heads high and briefly supporting on fore legs. They react with loud vocalization when disturbed even as newborns.
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Weasels are specialized carnivores, second only to cats. Their baby teeth, as well as the permanent teeth, are specialized for meat. The least weasel is most dependent on mice and rarely eats anything other than small rodents. They will often starve if the rodent population crashes, especially the females. The males are more willing to eat other foods. The long‐tailed weasel has the most varied diet of the weasels.
Feed a high quality kitten kibble such as Evo or Wilderness. Can start with smaller mice and work up (fuzzies => hoppers => juveniles/YA => adults Because of their high metabolism they require 5‐10 meals per day of a few grams/meal spaced 2 ½ ‐ 3 hours apart. Cannot consume more quantity/meal (ie, gorging) or eat more frequently even if underfed. Smaller animals require more food relative to size than larger ones. LW > STW > LTW; ♀ > ♂
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Evidence of nursing right up until dispersal.
Optimal survival was found for those released at 13‐18 weeks (the natural dispersion time) vs released at 20‐40 weeks. May be due to a window of opportunity to master survival skills such as hunting and predator avoidance.
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STW vs LW: initially the STW grew more slowly than the LW, catching up and passing the female LW @ 48‐52d and the male @ 55‐60d
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LTW started out with similar growth pattern but from a heavier starting point.
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Mice: gradually increase in size of mouse and size of chunks as indicated by the individual
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“latrine” areas facilitate spot cleaning; cardboard tubes are used to stash leftovers and easily replaced. Prey species so cover must be provided.
They hide in the paper tubes, making an easy route for capture (close of both ends of the tube and lift out).
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Weasels are specialized carnivores, second only to cats. Their baby teeth, as well as the permanent teeth, are specialized for meat. The least weasel rarely eats anything other than small rodents, if available, and will often starve if the rodent population crashes. The long‐tailed weasel has the most varied diet of the weasels.
Mustela as a rule show little or no avoidance behavior. They are the epitome ADD in the animal kingdom: high energy, very curious, easily distracted, and unintimidated by larger creatures (including humans).
Unless humans are threatening them, or threatening their food supply, the weasels often go about their business with no regard to the presence of people. If they feel threatened they may watch carefully from a safe vantage point and vocalize.
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Least weasel pre‐release enclosure. The tunnel system and logs were good; in the future I would add branches for additional top cover.
The least weasels did not have much interest in climbing but short‐ and long‐tailed weasels both need access to different levels – slings and hammocks, tree branches, etc.
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Need sufficient space, escape routes, and hiding places to help maintain predator avoidance strategies.
Captive mice offer no hunting challenge, but can help improve kill efficiency. Hunting experience: Perhaps live‐trapped wild mice (from houses?); allow the mouse/mice time in the cage prior to introducing weasel.
Weasels are scent hunters, and will often not notice prey that is above them and not moving (the mice would climb and then freeze to escape notice).
One hunting technique they use is to periodically dash around the enclosure/range to flush out mice.
Released at 12‐18 weeks, mimicking natural dispersion, had better survival than those released at 20‐40 weeks.
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A clever nest box that could be used for transport and soft release, and offering a place to leave food mice.
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Recommended vaccines and other medication used successfully listed on the handout.
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