The Implications of Coprophagy in Multiple Species

Coprophagy is the act of eating feces. This behavior is commonly seen in many

herbivorous rodents as well as some larger mammals. The biological reasons for the

development of this behavior are yet to be fully understood. There are numerous theories that

have been proposed for various species that exhibit coprophagy although extensive studies have

not been conducted in most cases. While the reason for the development of coprophagy is not

clear in all cases some of the nutritional benefits have been recorded as well as environmental

conditions that lead to the exhibition of this behavior. Even though coprophagy has been

observed in both small and large mammals, the technical details and the cycles that are followed

vary between species. We will be looking at some of these cases through the course of this paper.

There are two types of coprophagy, allocoprophagy and autocoprophagy.

Allocoprophagy is the consumption of the excrement of another individual while

autocoprophagy is when an individual ingests their own feces (Well, 2003). Both of these are

seen in nature, particularly among species that are primarily herbivorous but the occurrence of

these behaviors in domestic pets is often disturbing to the owners. There are multiple theories

about what causes coprophagy in domestic animals such as dogs. These range from behavioral

problems to medical issues or abnormalities. Some believe that an imbalanced diet or pancreatic

enzyme deficiency could result in this behavior as the animals attempt to acquire the proper

amount of nutrients. The alternate theory is that the behavior results from operant conditioning.

The dog was punished for eating feces but because of the attention that it received, although

negative, the behavior was reinforced. These animals persist in eating feces so as to get attention

from their owners (Well, 2003)

Since this behavior in domestic animals can be unhealthy different theories have

developed suggesting ways to stop or curb this habit. One study that was conducted compared

the effectiveness of two treatments commonly used by the public; the use of spray collars and

sound therapy. These methods are referred to as disruptive stimulants since they work to disrupt

the negative behavior and force the dog’s attention to something else. This particular study

showed that the spray collars had a longer effect on the individuals it was tested on. These dogs

responded to the treatment faster and refrained from coprophagy for a longer period of time after

the trials stopped. This method affects multiple senses, smell, hearing and touch, while the sound

affects only one. It is thought that this may be the reason for the difference in results. By

engaging multiple senses, the animal is able to learn faster and remember the training for a

longer period of time (Well, 2003).

These methods are a direct, physical way to change the dog’s behavior. If the coprophagy

is the result of a dietary or other physiological problem these methods will most likely fail.

Changing the diet to one that is rich in fat, protein and fiber but low in carbohydrates could

reduce the likelihood that the dog will look for an alternate food source and thus eat feces.

Lastly, it is also suggested that flavoring the feces with unpleasant but harmless substances will

aid in curbing the habit through counter-conditioning (Well, 2003).

While coprophagy is seen as a negative behavior in domestic animals there are many wild

animals that depend on coprophagy to survive. Some of these alter their eating habits to include

coprophagy when other food sources are scarce and others practice coprophagy on a daily basis

as a part of their natural metabolic cycles while still others exhibit this behavior only during

certain life stages.

Svalbard Reindeer on Spitsbergen are one example of a species that uses coprophagy to

cope with food shortages. Barnacle geese forage in the same habitat as these reindeer for part of

the year. Because of the digestive tract of the goose there is an ample amount of digestible

material in their droppings. Since the reindeer have a more complex gut they are able to

breakdown parts of the plant material that remains in the goose pellets.

While coprophagy was being practiced the animals still exhibited a food preference.

When they are able to forage on plants the reindeer prefer lichens before grasses and both of

these over mosses. This preference persisted into their practice of coprophagy. During a study,

goose droppings that contained different plant material were dispersed in an area. The reindeer

were then observed consuming these pellets and the pellets that were left behind were examined

to determine which plant material they contained. The geese consume grasses and mosses so the

pellets that the reindeer had to choose from contained one of these two materials. It was found

that the pellets containing mosses were refused while the reindeer consumed those containing the

grasses. The cause of this is thought to be the digestibility of the moss pellets. When examined,

the grass pellets had a digestibility that was very similar to that of the actual plant matter. The

preference may also be an adaptation to acquire certain minerals. Selection for potassium over

magnesium and sodium could explain the avoidance of mosses (Loonen et al., 1998).

In addition to this, the area in which this study was conducted had a forage content that

was restricted by the grazing of both the geese and the reindeer. Because of this, it was easy for

reindeer to consume enough feces to meet their energy requirements. In some scenarios where

reindeer would run-off sleeping geese they were able to acquire a substantial amount of energy

from the feces that had accumulated while expending a minimal amount of energy (Loonen et

al., 1998).

While the reindeer practice coprophagy to compensate for a shortage of forage material

other herbivores, such as the Degu, rabbit and the rat, use coprophagy in their daily metabolic

cycles. These species reingest a large amount of their feces each day although the cycles vary

between the species. Studies have been conducted investigating the different cycles and reasons

for coprophagy in these species.

The Degu is an herbivorous rodent that consumes abundant but low quality foods. They

are also hindgut fermenters that use microbial fermentation in their cecum to break down some

nutrients. Since this occurs in their hindgut the nutrients cannot be absorbed at this point so the

feces that are produced, which now contain these nutrients, must be reingested so that they can

go through the digestive system a second time and be absorbed. When observed, the Degu

practiced coprophagy during a resting period between feedings and at night. Coprophagy was

also observed when food was scarce. The Degu was also seen chewing each pellet that was

reingested while other species swallow the pellet whole with no chewing (Bozinovic et al., 1998)

As mentioned above, the Degu is a hindgut fermenter. It is believed that coprophagy in

this class of animals allows food to pass through the digestive system twice which results in the

possibility for increased absorption of nutrients (Lewin, 2001). The chewing of the pellet that is

observed in the Degu suggests that the fermentation did result in the release of more nutrients.

By practicing coprophagy during times of rest between feedings the Degu prevents the feces

from competing with food for time and space in the digestive system. While the Degu practices

coprophagy during these resting times it has been noted that the rate of coprophagic behavior is

increased in times when food is scarce and during the reproductive season. This is another

indication that nutrients are gained through this behavior which will provide the animal with

more energy to survive the stress successfully (Bozinovic et al., 1998).

The Degu is one of many rodents that practice coprophagy but the behavior is also seen

in numerous lagomorphs such as hares, rabbits and pika. In these species the pattern of feces

consumption varies from that seen in the Degu. Instead of consuming feces during the night

these species discharge pellets from the cecum during short periods in the morning and evening.

Each pellet is swallowed whole, contrary to the chewing behavior seen in the Degu (Bozinovik et

al., 1998).

Another example of a rodent practicing coprophagy is the Nutria. According to studies

conducted with this species it was found that coprophagy increases the digestibility of acid

detergent fiber and crude protein. This allows these animals and other rodents similar to them to

survive on low protein diets. In this case, feces were chewed before being consumed and the

individuals had a specific posture that they assumed before each act of coprophagy. The cycle of

coprophagic behavior involves vigorous eating and drinking after sunset followed by coprophagy

from midnight to noon (Sakaguchi, 1998).

Unlike some other species, the coprophagy cycles differ with age in the Nutria. Adult

animals spend much more time in this behavior then the young. Adult nutrias also began this

behavior before sunset without a visible cue. Another attribute unique to the Nutria is the

concentration of bacteria on a specific region of their hard feces while soft feces show distinct

compositional differences from these hard feces. The soft feces also contain more bacteria then

the hard feces. These feces are comparable to the rumen fluid of other animals and thus allow the

nutrias to absorb more protein while having the potential to release more amino acids into the

system (Sakaguchi, 1998).

Another species that practices coprophagy is the American Beaver. Reingestion in this

species begins at a young age, approximately ten days after birth, and is refined to a more

proficient process by the time the animal is twenty days old. In this species feeding and

defecation occur mostly during the early evening with the animal sleeping till mid-morning

before practicing coprophagy. This behavior was the strongest at mid-day and slowed in the

afternoon, alternating with sleep until feeding resumes in the evening (Buech, 1984).

The digestive system of the beaver is believed to process material in the following way,

food is partially digested as it passes through the stomach and small intestine. It is then passed to

the caecum which contains microorganisms that digest cellulose. After this, part of this material

is passed to the colon and reingested during the middle of the next day. This allows the small

intestine to absorb nutrients that are released by the caecal microbes (Buech, 1984).

Although coprophagy can function solely to recover nutrients it may also serve other

physiological functions. The digestive system of some young animals is dependent upon gut

flora that is obtained by consuming the feces of the parent animals (Lewin, 2001). In the case of

rats, coprophagy functions to recover compounds necessary to the proper functioning of their

biological systems (Ikeda et al., 2003). In order for the digestive systems of some animals to

become fully functional and able to handle the food consumed they must obtain particular gut

flora. This flora is obtained by consuming the feces of a parent which contain small samples of

these microbial compounds. The young can then retain this flora in their gut which allows them

to breakdown their food properly (Lewin, 2001).

In addition to this, rats produce two different types of feces, hydrous and normal. The

hydrous feces are those that are consumed when the animals practice coprophagy. The normal

feces are allowed to pass without being reingested. After examining the different types of feces it

was found that the hydrous feces contain significantly more sodium and potassium then the

normal variety as well as higher levels of protein, cyanocobalamin and folic acid. The sodium

and potassium cations have been shown to play a key role in the sodium-potassium pump that

functions to aid intestinal absorption and transport nutrients in the cells. These compounds are

also required for proper growth. If coprophagy is restricted in these animals there is not an affect

on food intake but on the absorption and use of nutrients in the food that is consumed. This,

therefore, results in vitamin deficiencies and reduced growth in the animals (Ikeda et al. 2003).

Rabbits practice coprophagy in a manner similar to that seen in rats. They also produce

two different types of feces, soft and hard, with the soft being immediately reingested (Boag et

al., 2004). While there is an emphasis on the reingestion of the soft feces the rabbits also reingest

the hard feces regularly. This results in a mix of isotopes from the dietary material in the stomach

that has been diluted by the consumption of the feces. The difference between the isotopic

content of the stomach and the fecal material indicates that the feces may have a role in

separating isotopes in these animals and thus altering their absorption in these animals (Boag et

al., 2004).

Although many animals practice coprophagy as a part of their metabolic cycles, this

behavior also results from some health problems such as exocrine pancreatic insufficiency. This

illness is common in many domestic animals as well as pigeons. An individual afflicted with this

illness experiences a loss of tubulo-acinar tissue due to inflammation or atrophy. This loss results

in an insufficient production and secretion of digestive enzymes and malabsorption. This

decreased absorption can lead to deficiencies in many vitamins, the effects of which depends on

the species that is ill and how the different vitamins are used by their system (Amann et al.,

2006).

Coprophagy is a behavior that is common among many wild animals although the basis

for this act varies. Many herbivores exhibit this behavior as a way to obtain more nutrients from

poor quality foods or to survive in harsh climates lacking the proper amount of forage. Some of

the species practicing coprophagy, such as many of the rodents, have digestive systems that are

modified specifically for coprophagy. These systems expel feces in different forms depending on

their content and potential use as a food source. Often times, one type of feces that is expelled

will be continuously consumed while the other type is discarded as waste.

While coprophagy is common in many herbivores it can also be observed in some

domestic animals such as dogs and other wild animals that must acquire gut flora from their

parent. This behavior is disturbing in the domestic breeds since it may lead to illness if the

individual consumes infested feces. Because of this many owners seek treatments to halt this

behavior and redirect the animal’s attention. The conditions that result in this behavior among

domestics is often similar to that seen when some wild animals practice this behavior such as

when they experience food stress.

Coprophagy has many biological and physiological functions. These range from the

obtainment of nutrients to the acquisition of particular minerals or gut flora. The behavior is

natural and serves a specific in each species that practices it. While this behavior is crucial to the

proper survival and growth of many species more studies need to be conducted to uncover all of

the implications of this behavior.

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