Osteophagy

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A bull chews on a bone of another cow. Bull chewing bone 4.jpg
A bull chews on a bone of another cow.

Osteophagy is the practice in which animals, usually herbivores, consume bones. Most vegetation around the world lacks sufficient amounts of phosphate. [1] Phosphorus is an essential mineral for all animals, as it plays a major role in the formation of the skeletal system, and is necessary for many biological processes including: energy metabolism, protein synthesis, cell signaling, and lactation. [2] Phosphate deficiencies can cause physiological side effects, especially pertaining to the reproductive system, [1] as well as side effects of delayed growth and failure to regenerate new bone. [2] The importance of having sufficient amounts of phosphorus further resides in the physiological importance of maintaining a proper phosphorus to calcium ratio. Having a Ca:P ratio of 2:1 is important for the absorption of these minerals, as deviations from this optimal ratio can inhibit their absorption. [3] Dietary calcium and phosphorus ratio, along with vitamin D, regulates bone mineralization and turnover by affecting calcium and phosphorus transport and absorption in the intestine. [4]

Contents

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 costly effects of deficiencies in these minerals. [1] Osteophagic behavior has been observed in pastoral and wild animals, most notably ungulates and other herbivores, for over two hundred years. [1] Osteophagy has been inferred from archaeological studies of dental wear in Pleistocene fossils dating back 780,000 years. [5] It has been seen in domestic animals, as well as red deer, camels, giraffes, wildebeest, antelopes, tortoises, and grizzly bears. [5] Due to differences in tooth structure, herbivores tend to chew old dry bones that are easier to break, while carnivores prefer to chew softer fresh bones. [6] Variations of the behavior have also been observed in humans.[ citation needed ]

While osteophagy has been regarded as a beneficial behavior to combat mineral deficiencies in animals, osteophagic practices have also been observed to be detrimental to the dentition of herbivores. It has been observed that the pattern of wear on the cheek teeth of herbivores is congruous to the manner in which herbivores hold and chew bones. [5] A major cost of osteophagy is therefore significant wear on teeth and dental breakage in herbivores, whose teeth did not evolve to enable the regular consumption of hard materials but rather for the grinding of vegetal fibers. [5]

Animals

Wolverine

Wolverines are observed finding large bones invisible in deep snow and are specialists at scavenging bones specifically to cache. Wolverine upper molars are rotated 90 degrees inward, which is the identifying dentition characteristic of the family Mustelidae (weasel family), of which the wolverine has the most mass, so they can crack the bones and eat the frozen marrow of large animals. This structural feature helps the wolverine be successful as a scavenger and adapt to a frozen habitat. [7]

Porcupine

Porcupine species including the largest, African porcupine and North American porcupine, are nocturnal bone collectors of thousands of bones, stored inside their den and in open piles in their vicinity. The bones do not satisfy seasonal nutritional deficiency, they prevent overgrown teeth but the shavings are ingested as the bulk of their diet. [8]

Tortoise

Osteophagy in desert tortoises has largely been observed in captivity, and more rarely in the wild where osteophagy observed above ground is quick and seldom, usually lasting only a few minutes. [9]

Desert plants are a major food source for desert tortoises (Gopherus agassizii), as they have a mainly herbivorous diet. [10] In addition to desert plants, desert tortoises also consume vulture feces (which contain bones), soil (layers contain calcium), mammal hairs, feathers, arthropods, stones, bones of conspecifics, as well as snake and lizard skin castings. [10] Desert tortoises have been observed to exhibit mounting behavior, aggressive biting, and repeated striking of carcasses when practicing osteophagy. [10]

Osteophagy in herbivores has been viewed to serve as a source for supplemental minerals. Desert plants grow in mineral-deficient soil, and may be a cause of mineral deficiency in desert tortoise diets, resulting in the intake of this supplemental material.

An observational study of tortoises near St. George, Utah, found that the tortoises exclusively consume the Mojave Desert's white stones, which are composed of calcite (mostly calcium carbonate), as opposed to the brown, grey, or other colored stones. [9] The ingestion of these white stones is attributed to the deliberate intake of additional calcium.

Furthermore, 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. [9]

It has also been hypothesized that osteophagy is a practice necessary for the maintenance of desert tortoise shells. [10] This parallels the phenomenon of osteophagy in birds, in which snail shells are ingested by egg-laying females to supplement the increased calcium needed for eggshell formation. Therefore, it would be expected that the increased physiological needs of juvenile and gravid female tortoises would also increase mineral demands and promote ingestion of bones, stones, and soil. 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. [10]

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 maize with unnaturally high levels of phosphorus, nearly eliminated botulism. The simplest conclusion for this was that the botulism symptoms were caused by a lack of phosphorus. [11]

In the early 1900s, Sir Thomas Thieler revisited the issue, and began following herds of cattle to observe their behavior. [12] 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. [11] The cattle would eat the carcasses to replenish their phosphorus deficiency, and would contract the disease.[ citation needed ]

More recently, in 2005, it was found that cows experimentally depleted of phosphate through the extended provision of a low-phosphate diet exhibited a specific appetite for bones compared to controls who did not develop an interest in bones. After researchers increased blood plasma inorganic phosphate levels in the experimental group of cattle, the appetite for whole bones was suppressed. This experiment provided evidence for the causal link between osteophagy and phosphorus deficiency in cattle. [1]

Bears

Grizzly bears in the wild have been observed to gnaw on shed moose antlers, which can provide a valuable source of protein, calcium, and phosphorus. [3]

Grizzly bears are at the weakest point into their annual cycle following emergence from hibernation, in terms of lacking mineral and protein nutrition. 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.[ citation needed ]

In winter conditions, while grizzly bears may be able to continue to maintain calcium intake with the ingestion of plants and maintain levels of vitamin D from solar radiation, low protein availability results in phosphorus deficiency in grizzly bear diets. This lack of protein during winter conditions can be attributed to the scarcity of animal proteins, a phenomenon that occurs in many ecosystems prior to green-up, or the ending of winter conditions. Therefore, overall, bones can serve as a valuable source of minerals at times where animal protein availability is low. [3]

The resulting phosphorus deficiency in grizzly bear diets results in a skewed calcium to phosphorus ratio and creates an appetite for bone. Because this deficiency is associated with the cycle of the seasons, osteophagy in bears is likely to be a seasonal phenomenon rather than a constant dietary supplement. [3]

Giraffes

Giraffes rely solely on browsing to maintain their diet, which consists primarily of leafy material. [13] However, they are commonly observed supplementing their diet with bones. [13] [14] 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. [13] While leaves usually serve as a sufficient source of these nutrients, calcium and phosphorus concentrations in the leaves vary seasonally with rainfall; the giraffes' osteophagic behavior has been observed to parallel this variance in mineral concentration. [13]

The benefits of this behavior remain unclear. Researchers have found that it is actually unlikely that the giraffes can sufficiently digest the bones to extract the calcium or phosphorus. [15] There is also evidence to suggest that osteophagy is associated with the development of kidney stones and medullary and cortical lesions in giraffes due to the nutritional imbalance in their diet. [13]

Domestic dog

While the media often portrays domestic dogs chewing bones, this is slightly misleading. Dogs chew bones only to eat any residual meat and bone marrow left on them, so it is not truly a form of osteophagy. [16] Most modern toy "bones" for dogs are actually rawhide, which is simply dried animal skin, as animal bones are actually dangerous for dogs to chew. [17]

Birds

Osteophagic behavior has been frequently observed among several carnivorous bird species including hawks and owls, however the motivations differ from those of the aforementioned herbivores. [18] Presumably, the bird's main purpose is to ingest the maximum amount of soft tissue from their prey as possible often resulting in the consumption of the prey's entire body. [18] The digestible materials are broken down while the indigestible material (i.e. bone) forms a pellet which is then regurgitated. [18] While the regurgitation of the bone is advantageous in that it frees space in the stomach for new prey, the behavior can be harmful in that the pellets are often larger than the digestive tract and could cause damage or obstruction. [18] In addition, the bearded vulture is a specialized bone-eater with bones making up 70–90% of its diet. [19]

Humans

Pica

Pica is the craving and consumption of non-nutrient substances that can cause health risks. [20] Osteophagy in humans would be considered a form of pica. Unlike calcium and phosphorus in most animals, pica is associated with iron deficiencies in humans. [21] Humans are unlikely to suffer from calcium and phosphorus deficiencies because the minerals are widely abundant in the foods they consume. [22]

Geophagy, the eating of earthen materials like clay, can be another form of pica that is more commonly observed than osteophagy. [21]

Religious practice

The Yanomami tribe live as nomads in the Brazilian and Venezuelan Amazon. [23] When a tribe member dies, it is a custom for their family to “set their spirit free” in a religious ritual. [23] During this ritual, the tribe grinds their bones to a fine ashen powder and mixes the powder into a plantain soup, which is eaten by the family of the deceased. [23] 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. [23]

See also

Related Research Articles

<span class="mw-page-title-main">Phosphorus</span> Chemical element, symbol P and atomic number 15

Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. In minerals, phosphorus generally occurs as phosphate.

<span class="mw-page-title-main">Eating</span> Ingestion of food

Eating is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbivores eat plants, omnivores consume a mixture of both plant and animal matter, and detritivores eat detritus. Fungi digest organic matter outside their bodies as opposed to animals that digest their food inside their bodies. For humans, eating is an activity of daily living. Some individuals may limit their amount of nutritional intake. This may be a result of a lifestyle choice, due to hunger or famine, as part of a diet or as religious fasting.

<span class="mw-page-title-main">Mineral (nutrient)</span> Chemical element required as an essential nutrient by organisms to perform life functions

In the context of nutrition, a mineral is a chemical element. Some "minerals" are essential for life, most are not. Minerals are one of the four groups of essential nutrients, the others of which are vitamins, essential fatty acids, and essential amino acids. The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium. The remaining elements are called "trace elements". They are iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine, and selenium.

<span class="mw-page-title-main">Plant nutrition</span> Study of the chemical elements and compounds necessary for normal plant life

Plant nutrition is the study of the chemical elements and compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or that the element is part of some essential plant constituent or metabolite. This is in accordance with Justus von Liebig’s law of the minimum. The total essential plant nutrients include seventeen different elements: carbon, oxygen and hydrogen which are absorbed from the air, whereas other nutrients including nitrogen are typically obtained from the soil.

<span class="mw-page-title-main">Osteomalacia</span> Softening of bones due to impaired bone metabolism

Osteomalacia is a disease characterized by the softening of the bones caused by impaired bone metabolism primarily due to inadequate levels of available phosphate, calcium, and vitamin D, or because of resorption of calcium. The impairment of bone metabolism causes inadequate bone mineralization. Osteomalacia in children is known as rickets, and because of this, use of the term "osteomalacia" is often restricted to the milder, adult form of the disease. Signs and symptoms can include diffuse body pains, muscle weakness, and fragility of the bones. In addition to low systemic levels of circulating mineral ions that result in decreased bone and tooth mineralization, accumulation of mineralization-inhibiting proteins and peptides, and small inhibitory molecules, can occur in the extracellular matrix of bones and teeth, contributing locally to cause matrix hypomineralization (osteomalacia/odontomalacia). A relationship describing local, physiologic double-negative regulation of mineralization has been termed the Stenciling Principle of mineralization, whereby enzyme-substrate pairs imprint mineralization patterns into the extracellular matrix by degrading mineralization inhibitors. The Stenciling Principle for mineralization is particularly relevant to the osteomalacia and odontomalacia observed in hypophosphatasia (HPP) and X-linked hypophosphatemia (XLH).

<span class="mw-page-title-main">Phytic acid</span> Chemical compound

Phytic acid is a six-fold dihydrogenphosphate ester of inositol, also called inositol hexaphosphate, inositol hexakisphosphate (IP6) or inositol polyphosphate. At physiological pH, the phosphates are partially ionized, resulting in the phytate anion.

<span class="mw-page-title-main">African spurred tortoise</span> Species of tortoise

The African spurred tortoise, also called the sulcata tortoise, is an endangered species of tortoise inhabiting the southern edge of the Sahara Desert, the Sahel, in Africa. It is the largest mainland species of tortoise in the world, and the third-largest in the world, after the Galapagos tortoise and Aldabra giant tortoise. It is the only living species in its genus, Centrochelys, with the five other species in the family already extinct.

Raw feeding is the practice of feeding domestic dogs, cats, and other animals a diet consisting primarily of uncooked meat, edible bones, and organs. The ingredients used to formulate raw diets vary. Some pet owners choose to make home-made raw diets to feed their animals but commercial raw diets are also available.

<span class="mw-page-title-main">Pagophagia</span> Medical condition

Pagophagia is the compulsive consumption of ice or iced drinks. It is a form of the disorder known as pica, which in Latin refers to a magpie that eats everything indiscriminately. Its medical definition refers to the persistent consumption of nonnutritive substances for over a period of at least one month. However, different studies have included alternative definitions including "daily consumption of 2-11 full glasses of ice (480-2640g)" or "the purposeful ingestion of at least one ordinary tray of ice daily for a period in excess of two months." Pagophagia has been shown to be associated with iron-deficiency anemia and responsive to iron supplementation, leading some investigators to postulate that some forms of pica may be the result of nutritional deficiency.

Bone meal is a mixture of finely and coarsely ground animal bones and slaughter-house waste products. It is used as a dietary supplement to supply calcium and phosphorus to monogastric livestock in the form of hydroxyapatite. As a slow-release organic fertilizer, it supplies phosphorus, calcium, and a small amount of nitrogen to plants.

<i>Gopherus</i> Genus of tortoises

Gopherus is a genus of fossorial tortoises commonly referred to as gopher tortoises. The gopher tortoise is grouped with land tortoises that originated 60 million years ago, in North America. A genetic study has shown that their closest relatives are in the Asian genus Manouria. The gopher tortoises live in the southern United States from California's Mojave Desert across to Florida, and in parts of northern Mexico. Gopher tortoises are so named because of some species' habit of digging large, deep burrows. Most notably, Gopherus polyphemus digs burrows which can be up to 40 feet (12 m) in length and 10 feet (3.0 m) in depth. These burrows are used by a variety of other species, including mammals, other reptiles, amphibians, and birds. Gopher tortoises are 20–50 cm (7.9–19.7 in) in length, depending on the species. All six species are found in xeric habitats. Numerous extinct species are known, the oldest dating to the Priabonian stage of the Late Eocene of the United States.

<span class="mw-page-title-main">Bladder stone (animal)</span> Common occurrence in animals

Bladder stones or uroliths are a common occurrence in animals, especially in domestic animals such as dogs and cats. Occurrence in other species, including tortoises, has been reported as well. The stones form in the urinary bladder in varying size and numbers secondary to infection, dietary influences, and genetics. Stones can form in any part of the urinary tract in dogs and cats, but unlike in humans, stones of the kidney are less common and do not often cause significant disease, although they can contribute to pyelonephritis and chronic kidney disease. Types of stones include struvite, calcium oxalate, urate, cystine, calcium phosphate, and silicate. Struvite and calcium oxalate stones are by far the most common. Bladder stones are not the same as bladder crystals but if the crystals coalesce unchecked in the bladder they can become stones.

<span class="mw-page-title-main">Equine nutrition</span> Feeding of domesticated equines such as horses, ponies, mules, and donkeys.

Equine nutrition is the feeding of horses, ponies, mules, donkeys, and other equines. Correct and balanced nutrition is a critical component of proper horse care.

Animal psychopathology is the study of mental or behavioral disorders in non-human animals.

Specific appetite, also known as specific hunger, is a drive to eat foods with specific flavors or other characteristics.

<span class="mw-page-title-main">Omnivore</span> Animal that can eat and survive on both plants and animals

An omnivore is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutrients and energy of the sources absorbed. Often, they have the ability to incorporate food sources such as algae, fungi, and bacteria into their diet.

Calcium acetate/magnesium carbonate is a fixed-dose combination drug that contains 110 mg calcium and 60 mg magnesium ions and is indicated as a phosphate binder for dialysis patients with hyperphosphataemia. It is registered by Fresenius Medical Care under the trade names Renepho (Belgium) and OsvaRen.

Inorganic feed phosphates (IFP) are inorganic salts of phosphoric acid. The use of inorganic feed phosphates is necessary to meet the phosphorus requirements for animal production: to ensure optimal growth, fertility and bone development.

Oral disease is one of the most common diseases found in dogs. It is caused by the buildup of various anaerobic bacteria in the mouth which forms plaque, eventually hardening into tartar on the teeth along the gum line, and is related to the development of gingivitis. Since small and toy breeds have a much smaller jaw but contain the same number of teeth, crowding allows higher bacterial build up and puts them at higher risk of developing periodontal disease.

A renal diet is a diet aimed at keeping levels of fluids, electrolytes, and minerals balanced in the body in individuals with chronic kidney disease or who are on dialysis. Dietary changes may include the restriction of fluid intake, protein, and electrolytes including sodium, phosphorus, and potassium. Calories may also be supplemented if the individual is losing weight undesirably.

References

  1. 1 2 3 4 5 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. doi:10.1002/bies.950040112. ISSN   1521-1878. PMID   3790111.
  2. 1 2 Penido, Maria Goretti M. G.; Alon, Uri S. (2012-11-01). "Phosphate homeostasis and its role in bone health". Pediatric Nephrology (Berlin, Germany). 27 (11): 2039–2048. doi:10.1007/s00467-012-2175-z. ISSN   0931-041X. PMC   3461213 . PMID   22552885.
  3. 1 2 3 4 Wald, Eric J. (2011). "Osteophagy by the Grizzly Bear, Ursus arctos". Northwest Science. 85 (3): 491–496. doi:10.3955/046.085.0307. S2CID   86699759.
  4. ↑ Masuyama, Ritsuko; Nakaya, Yumi; Katsumata, Shinichi; Kajita, Yasutaka; Uehara, Mariko; Tanaka, Shinya; Sakai, Akinori; Kato, Shigeaki; Nakamura, Toshitaka (2003-07-01). "Dietary calcium and phosphorus ratio regulates bone mineralization and turnover in vitamin D receptor knockout mice by affecting intestinal calcium and phosphorus absorption". Journal of Bone and Mineral Research. 18 (7): 1217–1226. doi:10.1359/jbmr.2003.18.7.1217. ISSN   0884-0431. PMID   12854831. S2CID   6712215.
  5. 1 2 3 4 Cáceres, Isabel; Esteban-Nadal, Montserrat; Bennàsar, Maria; Monfort, M. Dolores Marín; Pesquero, M. Dolores; Fernández-Jalvo, Yolanda (2013). "Osteophagia and dental wear in herbivores: actualistic data and archaeological evidence". Journal of Archaeological Science. 40 (8): 3105–3116. Bibcode:2013JArSc..40.3105C. doi:10.1016/j.jas.2013.04.006. hdl:10261/126236.
  6. ↑ Cáceres, Isabel; Esteban-Nadal, Montserrat; Bennàsar, Maria; Fernández-Jalvo, Yolanda (2011). "Was it the deer or the fox?". Journal of Archaeological Science. 38 (10): 2767–2774. Bibcode:2011JArSc..38.2767C. doi:10.1016/j.jas.2011.06.020.
  7. ↑ "Dentition of the Wolverine". The Wolverine Foundation. 2014-02-21.<
  8. ↑ Duthie, A.G.; Skinner, J.D. (1986). "Osteophagia in the Cape porcupine Hystrix africaeaustralis". South African Journal of Zoology. 21 (4): 316–318. doi: 10.1080/02541858.1986.11448005 .
  9. 1 2 3 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.
  10. 1 2 3 4 5 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. doi:10.1894/0038-4909(2007)52[147:obtdtg]2.0.co;2. JSTOR   20424802. S2CID   86207279.
  11. 1 2 Theiler, Sir Arnold (1927). "Lamsiekte (Parabotulism) in cattle in South Africa: osteophagia and phophorus deficiency in relation to lamsiekte". Onderstepoort Journal of Veterinary Research. hdl:2263/13209.
  12. ↑ Bigalke, R. D. (2012-10-08). "Lamsiekte (botulism): solving the aetiology riddle". Journal of the South African Veterinary Association. 83 (1): 508. doi: 10.4102/jsava.v83i1.508 . ISSN   1019-9128. PMID   23327122.
  13. 1 2 3 4 5 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. doi:10.2307/3800701. JSTOR   3800701.
  14. ↑ 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. Bibcode:2013JArSc..40.4139H. doi:10.1016/j.jas.2013.06.004.
  15. ↑ Bredin, I. P.; Skinner, J. D.; Mitchell, G. (2008-03-01). "Osteophagia provide giraffes with phosphorus and calcium?" (PDF). The Onderstepoort Journal of Veterinary Research. 75 (1): 1–9. doi: 10.4102/ojvr.v75i1.82 . ISSN   0030-2465. PMID   18575058.
  16. ↑ "Give Your Dog a Bone (A conversation with The Canine Coach on keeping your dog's teeth clean.)". sojos.com. 2011. Archived from the original on 2012-03-07.
  17. ↑ USPatent 6584938,"Dog bone with jerky pieces and method for making",published 2003
  18. 1 2 3 4 Myhrvold, Nathan P. (2012-10-01). "A call to search for fossilised gastric pellets". Historical Biology. 24 (5): 505–517. doi: 10.1080/08912963.2011.631703 . ISSN   0891-2963. S2CID   84027351.
  19. ↑ "Bearded vulture". wwf.panda.org. Archived from the original on 2021-02-21.{{cite web}}: CS1 maint: unfit URL (link)
  20. ↑ Khan, Yasir; Tisman, Glenn (2010-03-12). "Pica in iron deficiency: a case series". Journal of Medical Case Reports. 4: 86. doi: 10.1186/1752-1947-4-86 . ISSN   1752-1947. PMC   2850349 . PMID   20226051.
  21. 1 2 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. doi: 10.4103/2249-4863.152277 . ISSN   2249-4863. PMC   4366992 . PMID   25811011.
  22. ↑ "Mineral Deficiency - symptoms, meaning, Definition, Description, Demographics, Causes and symptoms, Diagnosis". www.healthofchildren.com. Retrieved 2015-11-19.
  23. 1 2 3 4 Jacob, Frank (2013-05-30). "They Eat Your Ash to Save Your Soul – Yanomami Death Culture". Academia.edu.
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