Foxes are very active creatures, hunting and storing food in preparation for the winter or if they have kits[1]. To maintain this lifestyle, a specific energy requirement must be met. As stated in a previous blog, the average nutrient intake for a red fox per day is around 470 Kcal[2]. To give further context to this number, an adult mouse would give around 60 Kcal, an egg would offer about 84 Kcal[2]. A fully grown red fox would have to eat about 8 mice per day to meet energy demands[2]. A study has shown, roughly 1 lb of food per day that needs to be eaten to meet the caloric demand[3]. This is to say, the red fox will eat up to approximately 10% of its body weight per day[3]. Shown in the study that the average required for adults and sub adults (6months- 1 year) was 520 grams[3]. A pregnant vixen will eat anywhere from 1.5 -2.5 times depending on the size and progress of the litter[1]. The weeks preceding birth, a vixen would need to intake roughly 700g of food[1]. Lactating vixens require twice the amount of food non-lactating vixens would need[1]. Red fox cubs require 130g of food in the first four weeks, increasing to 320g when they are six weeks old (weaned) and 440g when they are 3 months old[1]. In the paper, Harris and Baker described a litter of four red fox cubs consuming 570Kg of food between them in their first year[3]. Foxes have considerably smaller stomach to similar mammals (eg. Dogs), a fully grown adult will generally not consume more than 1.5lbs in one meal[3]. Since the main source of nutrient a fox will eat is protein, most of energy gained from food will be used to hunt more prey[4]. They have a faster metabolism than most other similar omnivores/carnivores[4]. This gives the red fox its lean build and swift movement to catch prey and run from predators[4]. Proportionally their BMR will be higher in summer time as opposed to in the winter, where they reduce energy expenditure and use up stored resources[5]. A study was done on Arctic foxes, a northern relative to the red fox, it showed that winter time BMR was 35Kcal/Kg/24h and rose to as high at 110Kcal/Kg/24 in summer[5]. This was the case as long as the fox was in its thermal neutral zone for all testing purposes[5].
References:
1. Lindstrom, Erik., 1988. Reproductive effort in the red fox, Vulpesv ulpes, and future supply of a fluctuating prey. Oikos. 52, 115-119.
2. " TABLES ." Nutrient Requirements of Mink and Foxes, Second Revised Edition, 1982 . Washington, DC: The National Academies Press, 1982 .
3. Von Schantz, Torbjorn, 1980. Prey consumption of red fox population in Southern Sweden. Biogeographica. 53-64.
4. Lanszki, J., heltai, M., 2002. Feeding habits of golden jackal and red fox in South-western Hungary During winter and spring. Mamm. Biol. 67, 129-136.
5. A, Gugołek., W, Zabłocki., D, Kowalska., P, Janiszewski., M, Konstantynowicz., ,. Strychalski., 2010. Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals. Arq. Bras. Med. Vet. Zootec.62, 948-953.
References:
1. Lindstrom, Erik., 1988. Reproductive effort in the red fox, Vulpesv ulpes, and future supply of a fluctuating prey. Oikos. 52, 115-119.
2. " TABLES ." Nutrient Requirements of Mink and Foxes, Second Revised Edition, 1982 . Washington, DC: The National Academies Press, 1982 .
3. Von Schantz, Torbjorn, 1980. Prey consumption of red fox population in Southern Sweden. Biogeographica. 53-64.
4. Lanszki, J., heltai, M., 2002. Feeding habits of golden jackal and red fox in South-western Hungary During winter and spring. Mamm. Biol. 67, 129-136.
5. A, Gugołek., W, Zabłocki., D, Kowalska., P, Janiszewski., M, Konstantynowicz., ,. Strychalski., 2010. Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals. Arq. Bras. Med. Vet. Zootec.62, 948-953.