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Osteophagy

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Osteophagy

Osteophagy is the practice whereby animals, usually but not always herbivores, consume bones. Most vegetation around the world lack sufficient amounts of phosphate.[1] Phosphate deficiencies can cause physiological side effects, especially pertaining to the reproductive system.[1] Osteophagic behavior has been observed in pastoral and wild animals for over two hundred years.[1] It has been suggested that osteophagy is an innate behavior that allows animals to supplement their phosphorus and calcium uptake in order to avoid the side effects of deficiencies.[1]

Contents

  • Animals 1
    • Turtles 1.1
    • Cattle 1.2
    • Bears 1.3
    • Giraffes 1.4
    • Domestic Dogs 1.5
  • Humans 2
    • Pica 2.1
    • Religious Practice 2.2
  • See also 3
  • References 4

Animals

Turtles

Desert plants are a major food source of desert tortoises, Gopherus agassizii, as they have a mainly herbivorous diet.[2] However, while desert plants are high in calcium content, desert tortoises have been observed to consume other substances which are also rich in calcium.[2] In addition to desert plants, desert tortoises also consume vulture feces (which contains bones), soil (layers contain calcium), mammal hairs, feathers, arthropods, stones, bones of conspecifics, as well as snake and lizard skin castings.[2] Desert tortoises have been observed to exhibit mounting behavior, aggressive biting, and repeated striking of carcasses when practicing osteophagy.[2] It is thought that these additional sources of food are sources of not only calcium, but also other nutrients including phosphorus, sodium, iron, copper, and selenium.[3] Desert plants grow in mineral-deficient soil, and may be a cause of mineral deficiency in desert tortoise diets, resulting in the intake of supplemental material.[3] It has also been hypothesized that osteophagy is a practice necessary for the maintenance of desert tortoise shells.[2] Alternatively, the need to consume supplemental minerals may serve the purpose of detoxifying plant compounds, or may serve other purposes not related to nutrition, such as to dislodge gut parasites.[2]

Cattle

In the late 1800s, a then relatively unknown disease called botulism was seen in very high levels in South African cattle, especially those that grazed in pastures with low phosphorus levels. Researchers found that feeding the cattle sterile bonemeal, or corn with unnaturally high levels of phosphorus, nearly eliminated botulism. The simplest conclusion for this was made: that botulism symptoms are caused by a lack of phosphorus.[4]

In the early 1900s, Sir Thomas Thieler revisited the issue, and began following herds of cattle to observe their behavior.[5] Incredibly, he found that the phosphorus-deficient cattle would eat the decomposing bones of dead cattle and other animals, and that this activity was highly correlated to botulism. Over the next several years, he was able to show that a bacterial strain living in the decomposing carcasses, Clostridium botulinum, was the true cause of the disease.[4] The cattle would eat the carcasses to replenish their phosphorus deficiency, and would contract the disease.

Bears

Grizzly bears (Ursus arctos), after emerging from hibernation, may be experiencing a skewed phosphorus-to-calcium ratio due to the lack of consumption of animal resources during the period of hibernation. In winter conditions, while grizzly bears may be able to maintain calcium intake and absorption due to ingestion of plants and vitamin D absorption from solar radiation, low protein availability results in phosphorus deficiency. This low protein availability is often the case prior to green-up in ecosystems.[6] Therefore, bones can serve as a valuable source of minerals at times where animal protein availability is low.[6]

Giraffes

Giraffes rely solely on browsing to maintain their diet, which consists primarily of leafy material.[7] However, they are commonly observed supplementing their diet with bones.[7][8] Although the exact purpose of this behavior is unknown, it is hypothesized that the ingestion of bones serves as an additional source of calcium and phosphorus.[7] While leaves usually serve as a proficient source of these nutrients, calcium and phosphorus concentrations in the leaves vary seasonally in correlation with rainfall; the giraffes' osteophagic behavior has been observed to parallel this variance in mineral concentration.[7]

The benefits of this behavior remain unclear. Researchers have found that is actually unlikely that the giraffes can digest the ingested bones sufficiently to extract the calcium or phosphorus.[9] There is also evidence to suggest that osteophagy is associated with the development of kidney stones in giraffes.[7]

Domestic Dogs

While the media often portrays domestic dogs chewing bones, this is slightly misleading. Dogs chew bones only to eat any residual meat left on them, so it is not truly a form of osteophagy. Most modern toy "bones" for dogs are actually rawhide, which is simply dried animal skin.

Humans

Pica

Pica is the craving and consumption of non-nutrient substances that can cause health risks.[10] Osteophagy in humans would be considered a form of pica. Unlike phosphorus in most animals, pica is associated with iron deficiencies in humans.[11] Geophagy, the eating of clay, is another form of pica that is more commonly observed.[11]

Religious Practice

The Yanomami tribe live as nomads in the Brazilian and Venezuelan Amazon.[12] When a tribe member dies, it is a custom for their family to “set their spirit free” in a religious ritual.[12] During this ritual, the tribe grinds/pulverizes their bones to a fine ashen powder and mixes the powder into a plantain soup, which is eaten by the family of the deceased.[12] It is possible that this ritual originated as a way to increase phosphorus and other minerals in the tribe’s diet, though it may just be a religious ritual without any other purpose.[12]

See also

References

  1. ^ a b c d Denton, D. A.; Blair-West, J. R.; McKinley, M. J.; Nelson, J. F. (1986-01-01). "Problems and paradigms: Physiological analysis of bone appetite (Osteophagia)". BioEssays 4 (1): 40–43.  
  2. ^ a b c d e f Walde, Andrew D.; Delaney, David K.; Harless, Meagan L.; Pater, Larry L. (2007-03-01). "Osteophagy by the Desert Tortoise (Gopherus agassizii)". The Southwestern Naturalist 52 (1): 147–149. 
  3. ^ a b Esque, Todd C.; Peters, Eric L. (1994). "Ingestion of bones, stones, and soil by desert tortoises" (PDF). Fish and Wildlife Research. Retrieved 2015-10-16. 
  4. ^ a b Theiler, Sir Arnold (1927). "Lamsiekte (Parabotulism) in cattle in South Africa: osteophagia and phophorus deficiency in relation to lamsiekte". Onderstepoort Journal of Veterinary Research. 
  5. ^ Bigalke, R. D. (2012-10-08). "Lamsiekte (botulism): solving the aetiology riddle". Journal of the South African Veterinary Association 83 (1).  
  6. ^ a b Wald, Eric J. (2011). "Osteophagy by the Grizzly Bear, Ursus arctos". Northwest Science 85 (3): 491–496.  
  7. ^ a b c d e Langman, V. A. (1978-01-01). "Giraffe Pica Behavior and Pathology as Indicators of Nutritional Stress". The Journal of Wildlife Management 42 (1): 141–147.  
  8. ^ Hutson, Jarod M.; Burke, Chrissina C.; Haynes, Gary (2013-12-01). "Osteophagia and bone modifications by giraffe and other large ungulates". Journal of Archaeological Science 40 (12): 4139–4149.  
  9. ^ Bredin, I. P.; Skinner, J. D.; Mitchell, G. (2008-03-01). "Osteophagia provide giraffes with phosphorus and calcium?". The Onderstepoort Journal of Veterinary Research 75 (1): 1–9.  
  10. ^ Khan, Yasir; Tisman, Glenn (2010-03-12). "Pica in iron deficiency: a case series". Journal of Medical Case Reports 4: 86.  
  11. ^ a b Kar, Sujita Kumar; Kamboj, Abhilove; Kumar, Rajesh (2015-01-01). "Pica and Psychosis – Clinical Attributes and Correlations: A Case Report". Journal of Family Medicine and Primary Care 4 (1): 149–150.  
  12. ^ a b c d "They Eat Your Ash to Save Your Soul – Yanomami Death Culture". www.academia.edu. Retrieved 2015-10-16. 


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