Malnutrition, hunger and thirst in wild animals

As explained in our section on the general reasons for wild animal suffering, animal populations will grow as much as they can until limiting factors put a stop to their growth. Generally, most of the decline in growth comes not from fewer animals being born, but from more animals dying. One of the most important factors limiting the growth of animal populations is the availability of food. In nature, animal populations generally reproduce at very high rates. However, many newborns die simply because they starve. Others survive initially but later die of starvation.

Food scarcity also leads to the deaths of many animals due to the simultaneous occurrence of hunger and predation. These two risks combine to reduce the ability of wild animals to thrive. How do hunger and predation relate? First, prey, naturally try to avoid predators as much as possible. This means they will try to find food in places in which the risks that predators pose to them are lower. For example, they will look for food in wooded areas where they can hide instead of in open plains where predators can more easily see them. This means that when there is not enough food in the areas in which they hide, they face hunger and malnutrition. When malnutrition becomes very severe and animals seriously risk starving they start leaving the wooded areas, increasing their vulnerability to predators. This leads to a rise in the number of deaths due to predation. So, predation and malnutrition combine to limit the growth of animal populations. The relationship between food availability and predation has been studied in detail, and there are many works published in scientific journals explaining how this happens in the cases of very different animals.1

Hunger and malnutrition also normally occur in populations that are not threatened by predators. Sometimes their effect is reduced because females suffering from malnutrition do not get pregnant. However, this does not eliminate the effects hunger has in these populations. Animals will normally reproduce and bring to life huge numbers of new sentient beings, much larger than the numbers required to replace their parents. The amount of food available for these newly born creatures will be a key factor that determines how many of them will survive. If the proper food requirements are not met for new populations of animals they will be unhealthy, and may not survive. Hence, food shortage is continuously a source of suffering for wild animals.

Thirst is another major contributor to high mortality rates in wild animals. There are two fundamental ways the lack of water leads wild animals to suffer and eventually to die in pain; First, during times of drought, there are not enough resources available for the large populations of animals. Scarcity of water may cause animals to simply die of thirst.2 Second, as in the case of malnutrition, some animals endangered by predators show a reluctance to seek water because of predatorial threat. They hide in safe places and stay there until they are so dehydrated that they cannot move. Thus they are unable to reach water and they die of thirst.3

Thirst is a frightening experience. It produces a sense of exhaustion caused by reduced blood volume and the body compensates for the lack of water by raising the heart and breathing rates. This dehydration leads to dizziness and collapse, and ultimately results in death.4

Thirst forces animals to take many risks to satisfy their profound need for water.5 Some animals eventually leave their hiding places despite their weakness from dehydration; however, they are already so debilitated that they become vulnerable prey at watering-holes full of predators and they end up dying from the attacks of predators as painfully as they would have from thirst.

The combination of thirst and starvation accelerates the process of dehydration that culminates in death. Many animals that live in arid conditions continue to feed as a survival strategy because there are some fluids in food. This allows the animal to remain alive for a longer period of time.6 Without the availability of water directly or indirectly through food many animals do not survive hostile climates.


Aiding animals suffering from hunger or thirst

There are often things we could do to prevent wild animals from dying due to malnutrition. Animals often starve in situations in which we could feed them or are at risk of dehydration when thirst could be alleviated.7 However, unless the animals in question belong to a species or subspecies that is considered to be “environmentally valuable,” they are commonly left to suffer without help.

Every now and then there are measures approved for the purpose of deliberately starving animals. This happens, for instance, in the case of urban pigeons. It is common for the authorities in a city to forbid feeding them.

We may want to help wild animals but, because of the way population dynamics works in the wild, we think helping them would make little impact in a meaningful way. One of the key factors limiting the growth of the wild animal population is access to food. If we feed all the animals and let none of them starve, they will all reproduce and their numbers will rise greatly in just a few generations. But this does not mean that suffering and massive death necessarily have to prevail in nature. It just means that any global solution to the widespread problem of starvation in nature will have to consider all these facts. A great deal of research remains to be done on this to figure out what can be done to help animals in ways that don’t make things worse in the long run for other animals. The point here is simply that if we reject speciesism, and if we accept that we should consider the interests of nonhuman animals, there is no reason not to act if we can do so without causing greater harm than good.

There are many examples of successful human interventions that help some wild animals, even if often the aims of the interventions are not to promote animal wellbeing but rather are guided by ecological goals, such as the preservation of a given species. For example, the management of wetlands for wild animals is usually done by means of construction of ponds8 or reed bed construction for water cleaning.9 This gives the animals in these areas regular access to water. These and other techniques could be used to help other animals in need of water. Such interventions could be monitored so they do not cause suffering to more animals (i.e. this may happen if ponds increase the population of insects, for instance, and due to their population dynamics, an increase in population necessarily leads to an increase in mortality). Despite known drawbacks and the current limitations of our knowledge, current techniques that help alleviate the distress of wild animals show that we can progress in helping animals in nature based on what we are already doing right now.

Further readings

Bright, J. L. & Hervert, J. J. (2005) “Adult and fawn mortality of Sonoran pronghorn”, Wildlife Society Bulletin, 33, pp. 43-50.

Creel, S. & Christianson, D. (2009) “Wolf presence and increased willow consumption by Yellowstone elk: Implications for trophic cascades”, Ecology, 90, pp. 2454-2466.

De Roos, A. M.; Galic, N. & Heesterbeek, H. (2009) “How resource competition shapes individual life history for nonplastic growth: ungulates in seasonal food environments”, Ecology, 90, pp. 945-960.

Hansen, B. B.; Aanes, R.; Herfindal, I.; Kohler, J. & Sæther, B.-E. (2011) “Climate, icing, and wild arctic reindeer: Past relationships and future prospects”, Ecology, 92, pp. 1917-1923.

Holmes, J. C. (1995) “Population regulation: A dynamic complex of interactions”, Wildlife Research, 22, pp. 11-19.

Huitu, O.; Koivula, M.; Korpimäki, E.; Klemola, T. & Norrdahl, K. (2003) “Winter food supply limits growth of northern vale populations in the absence of predation”, Ecology, 84, pp. 2108-2118.

Jędrzejewski, W.; Schmidt, K.; Theuerkauf, J.; Jędrzejewska, B.; Selva, N.; Zub, K. & Szymura, L. (2002) “Kill rates and predation by wolves on ungulate populations in Białowieża Primeval Forest (Poland)”, Ecology, 83, pp. 1341-1356.

Kirkwood, J. K. (1996) “Nutrition of captive and free-living wild animals”, in Kelly, N. C. & Wills, J. M. (eds.) Manual of companion animal nutrition & feeding, Ames: British Small Animal Veterinary Association, pp. 235-243.

Lochmiller, R. L. (1996) “Immunocompetence and animal population regulation”, Oikos, 76, pp. 594-602 [accessed on 18 February 2013].

McCue, M. D. (2010) “Starvation physiology: Reviewing the different strategies animals use to survive a common challenge”, Comparative Biochemistry and Physiology – A Molecular and Integrative Physiology, 156, pp. 1-18.

Messier, F. & Crête, M. (1985) “Moose-wolf dynamics and the natural regulation of moose populations”, Oecologia, 65, pp. 503-512.

Mykytowycz, R. (1961) “Social behavior of an experimental colony of wild rabbits, Oryctolagus cuniculus (L.) IV. Conclusion: Outbreak of myxomatosis, third breeding season, and starvation”, CSIRO Wildlife Research, 6, pp. 142-155.

Okoro, O. R.; Ogugua, V. E. & Joshua, P. E. (2011) “Effect of duration of starvation on lipid profile in albino rats”, Nature and Science, 9 (7), pp. 1-13 [accessed on 13 January 2013].

Punch, P. I. (2001) “A retrospective study of the success of medical and surgical treatment of wild Australian raptors”, Australian Veterinary Journal, 79, pp. 747-752.

Robbins, C. T. (1983) Wildlife feeding and nutrition, Orlando: Academic Press.

Tomasik, B. (2016) “How painful is death from starvation or dehydration?”, Essays on Reducing Suffering, Jan-Feb [accessed on 10 April 2016].

United States Department of Agriculture: Animal and Plant Health Inspection Service & Indiana Department of Natural Resources: Division of Fish and Widlife (2009) “Starvation and malnutrition in wildlife”, Indiana Wildlife Disease News, 4 (1), pp. 1-3 [accessed on 22 October 2014].

Wobeser, G. A. (2005) Essentials of disease in wild animals, New York: John Wiley and Sons.


1 See for instance: Anholt, B. R. & Werner, E.  E. (1995) “Interaction between food availability and predation mortality mediated by adaptive behavior”, Ecology, 76, pp. 2230-2234; McNamara, J. M. & Houston, A. I. (1987) “Starvation and predation as factors limiting population size”, Ecology, 68, pp. 1515-1519; Sinclair, A. R. E. & Arcese, P. (1995) “Population consequences of predation-sensitive foraging: The Serengeti wildebeest”, Ecology, 76, pp. 882-891; Anholt, B. R. & Werner, E. E. (1998) “Predictable changes in predation mortality as a consequence of changes in food availability and predation risk”, Evolutionary Ecology, 12, pp. 729-738 [accessed on 5 February 2013]; Sweitzer, R. A. (1996) “Predation or starvation: Consequences of foraging decisions by porcupines (Erethizon dorsatum)”, Journal of Mammalogy, 77, pp. 1068-1077; Hik, D. S. (1995) “Does risk of predation influence population dynamics? Evidence from cyclic decline of snowshoe hares”, Wildlife Research, 22, pp. 115-129; Anholt, B. R.; Werner, E. & Skelly, D. K. (2000) “Effect of food and predators on the activity of four larval ranid frogs”, Ecology, 81, pp. 3509-3521.

2 Nair, R. M. (2004) “Hunger and thirst haunt wildlife”, The Hindu, March 26 [accessed on 9 March 2013].

3 TNN (2010) “Starvation, thirst kill many antelope in Jodhpur”, The Times of India, Jul 4 [accessed on 24 February 2013].

4 Gregory, N. G. (2004) Physiology and behavior of animal suffering, Ames: Blackwell, p. 83.

5 As an illustration of this, see, for example, Shears, R. (2009) “Panic as 6,000 thirsty wild camels invade Australian outback town, smashing roads and houses”, Mail Online, 25 November [accessed on 11 March 2013].

6 Gregory, N. G. (2004) Physiology and behavior of animal sufferingop. cit., p. 84.

7 Some examples of this can be found here: Nepal Mountain News (2011) “Quenching wildlife thirst by pumping ground water”, Nepal Mountain News, 9 December [accessed on 12 February 2013]; and here: Work, A. (2011) “Birds need a lift: Thirst rises for wildlife in drought: Water supply wilts in heat wave”, Times Records News, 30 August [accessed on 13 February 2013].

8 Wildpro (2011a) “Pond construction – Concrete (managing wetlands for wildlife – implementing management plan)”, [accessed on 25 February 2013]; Wildpro (2011b) “Pond construction (synthetic liner) (managing wetlands for wildlife – implementing management plan)”, [accessed on 26 February 2013].

9 Wildpro (2011c) “Reedbed construction for water cleaning (managing wetlands for wildlife – implementing management plan)”, [accessed on 24 February 2013].

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