Food Habits
WHAT do River Otters eat?
In the study conducted by 1954 in a comparison of Mink and Otter diets, obtained the average overal feed consumption of River Otters using a Scat Analysis to identify specific prey consumed.
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Gallery of a few of the key food items in the River Otters diet
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HOW do River Otters obtain their food?
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WHEN do river otters eat?
** seasonality has a large impact on the prey and diet of the River Otter, in turn this has en effect on the nutritional intake and metabolizable energy -- see energy requirements |
Graph from Stearns and Serfass (2010), illustrates the variation in crayfish and fish diets of the River Otter with the changing season at two different locations, the high levels of fish consumption in the spring being attributed to slow moving, lethargic fish as a result of stressful spawning.
Location and seasonality impact on piscivore diet - In a piscivorous diet as well the otters use auto-enzymatic digestion that to extract the nutrients from the prey, oily fish having a higher fat content stored in their muscles in high quantity pre-spawning and low quantity post spawning (when they are most susceptible to predation by otter species) , and non oily fish have the fat content stored primarily in their liver, having a higher fat content in warmer colder waters than warmer waters due to the the higher fat content in the food chain in colder climates (Esther Finegan Lecture Notes 2014). Since Otters consume their entire prey the timing (breeding season) and temperature (season and location in north america) are the primary factors determining gross energy received from their prey. |
Nutritional Value of Food
A study on river otters by White et al. 2007 in captivity showed the greatest digestive efficacy and nutrient absorption on a diet that his high protein, high fat and enough caloric intake to sustain the otters high metabolic rate
Table from Henry et al. 2012 illustrating the target nutrient ranges for a vareity of otter species in general based on captive animal values from in situ and ex situ diet comparisons
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Sample diet composition of Captive River Otter
- based on dry matter basis and analysis - varies for wild otter species depending on subspecies, age -Based on the study by White et al. 2007, the river otter had the highest digestible efficiency when consuming a high gross energy diet with a high water content, the results were measure using fecal samples on captive North American River Otters in Nebraska - Think mink diet is also another common carnivorous diet that many otter species respond well to in terms of metabolic maintenance and digestive efficacy (Henry et al. 2012). |
** NOTE: Nutritional requirements for wild species are difficult to determine as they require feces, urine, and blood samples and tested in a laboratory setting, therefore a lot of the information on the nutritional requirements come from captive animals and then speculation is made for wild species, in addition a large majority of carnivorous diets are analyzed using the typical feline diet and nutritional requirements as an additional reference.
** Main references for this page
1. Henry, B., Maslanka, M., Heuer, K., Reed-Smith, J., and Nidasio, G. (2012) Otters in zoo, aquaria, rehabilitation and wildlife sanctuaries. IUCN River Otter Specialist. Available: http://www.otterspecialistgroup.org/Library/TaskForces/OCT.html [March 2, 2014].
2. Reed-Smith,J . (2012). North american river otter. Husbandry Notebook, Edition 4. (Chapters 1-6).
3. Stearns, C.R. and Serfass, T.L. (2010). Food habits and fish prey size selection of a newly colonizing population of river otters (Lontra Canadensis) in eastern north dakota. Am. Midl. Nat. 165: 169-184.4.White, S.C., Clark, D.W., Day, C.D., Sikes, R.S. (2007) Variation in digestive efficiency of captive north american river otters (Lontra Canadensis) on various diets. Zoo Biology. 26: 41-50.
1. Henry, B., Maslanka, M., Heuer, K., Reed-Smith, J., and Nidasio, G. (2012) Otters in zoo, aquaria, rehabilitation and wildlife sanctuaries. IUCN River Otter Specialist. Available: http://www.otterspecialistgroup.org/Library/TaskForces/OCT.html [March 2, 2014].
2. Reed-Smith,J . (2012). North american river otter. Husbandry Notebook, Edition 4. (Chapters 1-6).
3. Stearns, C.R. and Serfass, T.L. (2010). Food habits and fish prey size selection of a newly colonizing population of river otters (Lontra Canadensis) in eastern north dakota. Am. Midl. Nat. 165: 169-184.4.White, S.C., Clark, D.W., Day, C.D., Sikes, R.S. (2007) Variation in digestive efficiency of captive north american river otters (Lontra Canadensis) on various diets. Zoo Biology. 26: 41-50.