Above: A North American river otter grasps its prey.
(North American river otter, Kevin Shafer, www.arkive.org) Lontra Canadensis
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Above: A mother European otter feeds on flatfish with her pups.
(European river otter, Jack Chapman, www.arkive.org) Lutra lutra |
Welcome to our page on the nutrition and energy needs of the North American river otter and the European river otter. Both Lontra canadensis and Lutra lutra are piscivorous, meaning their diets consist largely of fish and other seafood, but they are also largely opportunistic (Clavero et al., 2003)(Crowley et al., 2013). This makes for an interesting array of food choices, so enjoy perusing the nutrition of these two species!
Prey of Choice
In a study conducted by Stearns and Serfass, otter spraints were collected and the remnants of prey items were assessed. The scats were collected from the Red River Valley region of North Dakota. The following is a summary of the percentage of scats that contained each prey item:
Fish: 83% Crayfish: 51.1% Insects: 26.7% Birds: 7.9% Amphibians: 6.7% Mammals: 6.0% Freshwater Mussels: 0.2% Fish and crayfish were the most common food sources, with crayfish being much more common than in the diet of the European river otter. There was also a distinct difference in the species of fish that accounted for the most common prey. Cyprinidae fish such as carp and minnows were in 64.7% of all scats and catfish was in 17.4%. (Stearns and Serfass, 2011) |
Prey of Choice
One Portugese study reported 36 different prey items from a collection of 916 Lutra lutra scats collected from reservoirs. The scats were then assessed to determine what percentage of the scats contained various animal remains. The following is a summary of the animal remains found in these scats:
Fish:79% Crustaceans:15.8% Insects: 2.8% Amphibians: 0.63% Reptiles: 0.55% Birds: 0.51% Mammals: 0.75% Of these categories, fish was the most common food source and the prevalence of certain fish was further noted. Of the fish found in scats, the most common by far was Lepomis gibbosus at 60.30%, with a distant second being Micropterus salmoides at 4%. (Sales-Luis, 2007) |
Seasonal Variation in Prey Consumption
In a study conducted by Crowley et al. in British Columbia, the frequency of prey consumption across seasons was recorded. They then categorized their findings into fish consumption by season and non-fish prey consumption by season.
A notable drop in sucker fish consumption occurrs in late August, which might be due to the increase in salmonid prevalence. This second graph displays the non-fish prey prevalence in the diet of the North American river otter.
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Seasonal Variation in Prey Consumption
In the same study as referenced above, seasonal variations of the noted prey items were recorded. The charts below entitled "Seasonal and spatial comparisons (χ2 with Yate's correction for continuity) of the diet (percent occurence) of Eurasian otters at the Aguieira reservoir" are adapted from their report and outline the seasonality of the major food sources utilized by Lutra lutra.
Each of the most popular fish species are outlined individually, in addition to the groups of less common prey items. (Sales-Luis et al., 2003)
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Feed Transit Time
In a study conducted by Davis et al., dyes were provided to 12 male North American river otters, in a diet consisting of mink cereal, ocean fish scraps, poultry byproducts, beef liver, and eggs. Transit time was then recorded by waiting for the appearance of dye within scats. In the two trials conducted, the mean transit time was determined to be 202 minutes, with the total transit times ranging from 135-300 min. (Davis et al., 1992)
Nutrient Content of
Common Food Sources Trout
All values are given on an 'dry matter basis' Crude Protein (CP) = 55.8% Fat (EE) = 34.5% Carbohydrates (NFE) = N/A Gross Energy (GE) = 6.5 kcal/g (Reed-Smith, 2001) Capelin
All values are given on an 'dry matter basis' Crude Protein (CP) = 59.8% Fat (EE) = 14.8% Carbohydrates (NFE) = N/A Gross Energy (GE) = 5.5 kcal/g (Reed-Smith, 2001) |
Nutrient Content of
Common Food Sources Gibel carp (Carassius auratus gibelio)
All values are given on an 'as fed basis' Crude Protein (CP) = 14.59 g/100g Fat (EE) = 4.16 g/100g Carbohydrates (NFE) = 3.18g /100g Metabolizable Energy (ME) = 491.86 kJ/100g (Lanszki et al., 2006) Edible Frog (Rana esculenta)
All values are given on an 'as fed basis' Crude Protein (CP) = 14.81 g/100g Fat (EE) = 1.21 g/100g Carbohydrates (NFE) = 3.07 g/100g Metabolizable Energy (ME) = 348.94 kJ/100g (Lanszki et al., 2006) |
Note:Carbohydrate and metabolizable energy values were not available for the North American river otter. Due to their close relationship to the European river otter, their metabolism of food is likely similar.
BMR
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BMR
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The standard calculation for basal metabolic rate in mammals is:
however, North American river otters' BMR can be determined by a slightly modified version of this calculation:
where W=mass of the animal in kg, and BMR is measured in kJ/kg. (Reed-Smith, 2001)
Taking the average weight of a female North American river otter, 8 kg, and substituting this into the calculation for BMR, we can calculate an average female's basal metabolic rate.
BMR= 84.6 (8)^0.78(+0.15)
BMR= 428.5 kJ/kg |
In a study by J.A. Iversen, it was determined that the BMR for mustelids over 1 kg can be calculated using the modified BMR equation:
This is the same equation utilized in the North American river otter. Therefore, these otters have the same energy requirements per kilogram of weight.(Iversen, 1972)
Taking the average weight of a female European river otter, 7 kg, and substituting this into the calculation for BMR, we can calculate an average female's basal metabolic rate.
BMR= 84.6 (7)^0.78(+0.15)
BMR= 386.1 kJ/kg |
Daily Energy Expenditure (DEE)
In order to calculate daily energy expenditure, basal metabolic rate can be multiplied by the standard for eutherian animals, 2.3.
Using the BMR calculated above:
DEE= BMR x 2.3 DEE= 428.5 kJ/kg x 2.3 DEE= 985.6 kJ/day |
Using the BMR calculated above:
DEE= BMR x 2.3 DEE= 386.1 kJ/kg x 2.3 DEE= 888 kJ/day |
Food Consumption to Meet
Energy Needs As noted above, a food source with metabolizable energy data was unavailable for the North American river otter, so the Gibel carp will be used as an example for meeting their energy needs.
ME (carp)= 491.86 kJ/100g
DEE= 985.6 kJ/day DEE/ME= 2 100g carp per day In order for an 8 kg female North American river otter to meet its daily energy needs, it needs to eat 2 100g carp per day.
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Food Consumption to Meet
Energy Needs Using the Gibel carp as an example food source, food consumption needs can be met in a 7kg female, European river otter.
ME (carp)= 491.86 kJ/100g
DEE= 888 kJ/day DEE/ME= 1.8 100g carp per day In order for an 7 kg female European river otter to meet its daily energy needs, it needs to eat 1.8 100g carp per day.
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Toxicity and Deficiency
Hypovitaminosis A
Studies on the effects of organochlorine pesticides and PCBs have included investigation on their influence on the concentration of vitamin A in the body. In a study by Williams et al., the eyes of 88 European river otters were collected in order to find signs of retinal dysplasia secondary to hypovitaminosis A and prolonged PCB and organochlorine exposure. Out of the 131 eyes collected, only 32 of these didn't show some sign of histological or gross abnormality. These abnormalities are indicative of hypovitaminosis A. Higher concentrations of dieldrin (an organochlorine pesticide) were found in the otters with dysplastic retinas. The researchers made note of some reproductive symptoms of hypovitaminosis A including: fetal resorption, abortion, stillbirth, abnormal bone remodelling, hydrocephalus, gonadal hypoplasia, and cryptorchidism. (Williams et al., 2004)
Studies on the effects of organochlorine pesticides and PCBs have included investigation on their influence on the concentration of vitamin A in the body. In a study by Williams et al., the eyes of 88 European river otters were collected in order to find signs of retinal dysplasia secondary to hypovitaminosis A and prolonged PCB and organochlorine exposure. Out of the 131 eyes collected, only 32 of these didn't show some sign of histological or gross abnormality. These abnormalities are indicative of hypovitaminosis A. Higher concentrations of dieldrin (an organochlorine pesticide) were found in the otters with dysplastic retinas. The researchers made note of some reproductive symptoms of hypovitaminosis A including: fetal resorption, abortion, stillbirth, abnormal bone remodelling, hydrocephalus, gonadal hypoplasia, and cryptorchidism. (Williams et al., 2004)
Thiamin Deficiency
Though no studies on thiamin deficiencies in otters have been brought to my attention, thiamin deficiency has been reported in other fish-eating animals, including the otters close relative, the mink. Due to the presence of thiaminases in many fish products, thiamin deficiency can occur and should be supplemented within the diet of otters when possible. (Reed-Smith, 2001)
Vitamin E Deficiency
Vitamin E deficiency is a common occurrence in fish-based diets due to the necessary breakdown of mono- and poly-unsaturated fatty acids. The process of breaking these down utilizes and destroys vitamin E. The outcomes of hypovitaminosis E in mammals can include: severe edema, nutritional muscular dystrophy, haemolytic anemia, and reproductive failure, and as such, vitamin E may need to be supplemented in otter diets. (Reed-Smith, 2001)
Though no studies on thiamin deficiencies in otters have been brought to my attention, thiamin deficiency has been reported in other fish-eating animals, including the otters close relative, the mink. Due to the presence of thiaminases in many fish products, thiamin deficiency can occur and should be supplemented within the diet of otters when possible. (Reed-Smith, 2001)
Vitamin E Deficiency
Vitamin E deficiency is a common occurrence in fish-based diets due to the necessary breakdown of mono- and poly-unsaturated fatty acids. The process of breaking these down utilizes and destroys vitamin E. The outcomes of hypovitaminosis E in mammals can include: severe edema, nutritional muscular dystrophy, haemolytic anemia, and reproductive failure, and as such, vitamin E may need to be supplemented in otter diets. (Reed-Smith, 2001)
Reproductive nutrition
Energy Requirements
The energy requirements for pregnant females are 17-32% than that of non-pregnant females.
Using the same 8kg female as above, if she were pregnant, her energy needs would go from 985.6 kJ/day to at least 1153.2 kJ/day! (Reed-Smith, 2001) |
Energy Requirements
The European river otter to intake 28% of its body mass in food per day during lactation to meet its energy needs. This is signficantly heightened, as the same source quotes 15% as the average daily intake of a non-lactating, non-pregnant female. (Kruuk, 2006)
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Milk Composition
As a typical mammalian species, the composition of milk is highly important to the development of otter pups. North American river otter milk is 62% water, 24% fat, 11% protein, 0.1% carbohydrates and 0.75% ash, which sustains the pups for the first 9-10 weeks of life. (Miller Ben Shaul, 1963)
For more information on reproduction in Lontra canadensis and Lutra lutra, please visit our Reproduction page!
Nutrition for Growth
Energy Requirements
Weaned river otters require high protein to meet their energetic demands for growth. For the average adult carnivore, 18-30% dietary protein is required for maintenance. In a growing, weaned carnivore, these values go up to 35%, with mink requiring 25-38% dietary protein. This is likely indicative of the protein requirements by growing otters, as mink are closely related. (Reed-Smith, 2001)
Energy values were not available for growth in either the North American river otter or the European river otter, but these would be heightened similarly to those of a pregnant or lactating female.
Energy values were not available for growth in either the North American river otter or the European river otter, but these would be heightened similarly to those of a pregnant or lactating female.
References
1. Arkive. 2015. Common otter (Lutra lutra). Available: http://www.arkive.org/common-otter/lutra-lutra. Accessed March 2, 2015.
2. Arkive. 2015. North American otter (Lontra canadensis). Available: http://www.arkive.org/north-american-otter/lontra-canadensis. Accessed March 2, 2015.
3. Clavero, M., J. Prenda, and M. Delibes. 2003. Trophic diversity of the otter (Lutra lutra l.) in temperate and Mediterranean freshwater habitats. J. Biogeogr. 30: 761-769.
4. Crowley, S., C.J. Johnson, and D.P. Hodder. 2013. Spatio-temporal variation in river otter (Lontra canadensis) diet and latrine site activity. Ecoscience. 20(1): 28-39.
5. Davis, H.G., R.J. Aulerich, S.J. Bursian, J.G. Sikarskie, and J.N. Stuht. 1992. Feed consumption and food transit time in northern river otters (Lutra canadensis). J. Zoo. Wildl. Med. 23(2): 241-244.
6. Iversen, J.A. 1972. Basal energy metabolism of mustelids. J. Comp. Physiol. 81(4): 341-344.
7. Kruuk, H. 2006.Otters ecology, behaviour and conservation.Oxford University Press, New York, NY.
8. Lanszki, J., M. Molnar, and T. Molnar. 2006. Factors affecting the predation of otter (Lutra lutra) on European pond turtle (Emys orbicularis). J. Zool. 270: 219-226.
9. Miller Ben Shaul, D. 1963. The composition of the milk of wild animals. Int. Zoo. Yearb. 4(1): 333-342.
10. Sales-Luis, T., N.M. Pedroso, and M. Santos-Reis. 2007. Prey availability and diet of the Eurasian otter (Lutra lutra) on a large reservoir and associated tributaries. Can. J. Zool. 85: 1125-1135.
11. Stearns, C.R. and T.L. Serfass. 2011. 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.
12. Reed-Smith, J. 2001. North American river otter. 2nd ed.
13. Williams, D.L., V.R. Simpson, and A. Flindall. 2004. Retinal dysplasia in wild otters (Lutra lutra). Vet. Rec. 155: 52-56.
2. Arkive. 2015. North American otter (Lontra canadensis). Available: http://www.arkive.org/north-american-otter/lontra-canadensis. Accessed March 2, 2015.
3. Clavero, M., J. Prenda, and M. Delibes. 2003. Trophic diversity of the otter (Lutra lutra l.) in temperate and Mediterranean freshwater habitats. J. Biogeogr. 30: 761-769.
4. Crowley, S., C.J. Johnson, and D.P. Hodder. 2013. Spatio-temporal variation in river otter (Lontra canadensis) diet and latrine site activity. Ecoscience. 20(1): 28-39.
5. Davis, H.G., R.J. Aulerich, S.J. Bursian, J.G. Sikarskie, and J.N. Stuht. 1992. Feed consumption and food transit time in northern river otters (Lutra canadensis). J. Zoo. Wildl. Med. 23(2): 241-244.
6. Iversen, J.A. 1972. Basal energy metabolism of mustelids. J. Comp. Physiol. 81(4): 341-344.
7. Kruuk, H. 2006.Otters ecology, behaviour and conservation.Oxford University Press, New York, NY.
8. Lanszki, J., M. Molnar, and T. Molnar. 2006. Factors affecting the predation of otter (Lutra lutra) on European pond turtle (Emys orbicularis). J. Zool. 270: 219-226.
9. Miller Ben Shaul, D. 1963. The composition of the milk of wild animals. Int. Zoo. Yearb. 4(1): 333-342.
10. Sales-Luis, T., N.M. Pedroso, and M. Santos-Reis. 2007. Prey availability and diet of the Eurasian otter (Lutra lutra) on a large reservoir and associated tributaries. Can. J. Zool. 85: 1125-1135.
11. Stearns, C.R. and T.L. Serfass. 2011. 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.
12. Reed-Smith, J. 2001. North American river otter. 2nd ed.
13. Williams, D.L., V.R. Simpson, and A. Flindall. 2004. Retinal dysplasia in wild otters (Lutra lutra). Vet. Rec. 155: 52-56.
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