Written by Christian Schiffmann & Marcus Clauss
Contents of this chapter:
General feeding ecology and feeding behaviors
Both elephant species are herbivores and consume a wide variety of plant material including grasses, leaves, twigs, fruits, barks, herbaceous material and soil (Sukumar 1990; Kabigumila 1993). A thorough review of diet breakdown, feeding behaviour, seasonal variation and summary data on broad nutrient ranges in natural diets for African elephants (Loxodonta africana) is covered in Sach et al. (2019). Variance between species does occur, with Asian elephants consuming a greater proportion of grasses in the diet when available (Sukumar 1990; Cerling et al. 1999). However, in our view, this does not mean that elephant species should be considered fundamentally different in their nutritional ecology.
Although described as generalist herbivores, consuming over 400 species of plants, it appears populations may vary regionally and seasonally in their plant choice. However, it is clear that elephants are predominantly seasonal grazers and browsers with fruit, barks and soil being consumed as secondary food choices (Kabigumila 1993). The natural diet is characterised by a high fibre content (crude fibre 30-50%) and a low to moderate protein content (crude protein 8-12%). In summary, elephants are designed to eat large quantities of nutrient poor fibrous material which passes quickly through the gastrointestinal tract.
Several studies indicate free living elephants of both species spend a considerable proportion (48-76.4%) of their day feeding, although where feeding conditions are improved and food availability increased, elephants have been seen to reduce the total amount of time spent feeding (Dougall and Sheldrick 1964; Beekman and Prins 1989). There is debate surrounding the feeding pattern; several reports indicate that elephants feed almost continuously throughout a 24-hour period (Laws 1970; Beekman and Prins 1989). However, there is also evidence that elephants feed in distinct peaks (Sukumar 1990). It is thought the feeding pattern may vary depending upon food availability, temperature (time spent in shade) and migration (usually to water).
It has been suggested that free-ranging elephants make use of specific sites where they eat soil (geophagy) in order to cover their nutritional requirements of minerals (Holdo et al. 2002; Holdo and McDowell 2004).
The body weight ranges overlap; however, Asian elephants (Elephas maximus) tend to be lighter than African elephants (Loxodonta africana). The weight range of wild adult Asian elephants is 1,800-5,000 kg compared with a range of 2,700-6,000 kg for adult African elephants (Wittemyer 2011). Individual body weights are influenced by age, sex, health, food availability and according to recent findings by the molar state (Schiffmann et al. 2019b).
With respect to their high-fibre and low-energy diet, elephants express a relatively high daily dry matter intake of 1-2% of body weight (Ullrey et al. 1997; Clauss et al. 2003). Feeding trials have shown a significantly reduced digestibility in elephants compared to horses (Clauss et al. 2003). Although heavily dependent on the provided diet, digestibility in elephants seems to range between 40 and 60% of dry matter. But even a digestibility as low as 22-32% has been detected in free-ranging African elephants (Rees 1982). According to an experimental study, digestibility decreases with increasing fiber content of an elephant’s diet (Clauss et al. 2003). Studies have demonstrated that passage of food through the elephant’s digestive tract is rapid compared to other monogastric hindgut digesters such as horses. Total gut transit time is 11-46 hours (Bax and Sheldrick 1963; Rees 1982; Hackenberger 1987; Loehlein et al. 2003), and they have a correspondingly low digestive efficiency (Clauss et al. 2003; Hatt and Clauss 2006). Elephants have a single stomach and a short but voluminous hindgut fermentation chamber (similar to equids), inhabited by anaerobic bacteria and protozoa similar to those found in the rumen and reticulum of the ruminant. These micro-organisms digest plant fibre that otherwise could not be used, since elephants, like other herbivores, have no fibre-digesting enzymes of their own (Ilmberger et al. 2014). Microbial fermentation of plant fibre in the hindgut provides the main energy source for these animals. They are adapted to eat complex plant fibres and thus in captivity, high fibre components must contribute a very significant part of their diet. As herbivores, elephants fulfil their needs in vitamins through their plant diet. This is the case for fat soluble as well as water soluble vitamins. Our knowledge on vitamin nutrition in elephants is still very limited and further research is needed (Fowler and Mikota 2006).
Body mass (BM, kilograms) and length measurements (meters) of an African (Loxodonta africana) and Asian (Elephas maximus) elephant (Clauss et al. 2007).
Nutritional management of elephants in captivity
and recommendations for feeding
Within each zoo, captive elephant diets should be formulated in line with the zoo’s dietary management programme using the skills of zoo nutritionists, curators, veterinary staff and keepers. The diet should be reviewed at least annually by appropriate staff, and proposed modifications raised in line with the individual institution’s diet management strategy. Forage consisting of grass, hay and browse should be the staple dietary ingredient, comprising a minimum of 80% of the total dry matter (Ullrey et al. 1997). Nutritionally appropriate pellets should be fed according to the individual dietary needs, but in the range of no more than approx. 20% of the total dry matter. Exceeding this may lead to excess energy consumption. Dietary items that deliver readily digestible energy, such as grains, bread, fruits, vegetables and low-fibre pellets should not be used in any significant quantity, although they may have uses for the administration of medication, or in geriatric animals. We want to emphasize that training should generally not be used as an excuse to feed unnatural feeds such as bread, fruits or sweets, and that training can often be done successfully using fresh green vegetables as well. This is not because a single piece of fruit is dangerous, but because often, one excuse leads to another. Excluding these items as training incentives is thus based on the concern about dietary drift. All food fed to the animal as part of the daily routine as well as used for training, enrichment or public activities must be included in the daily diet ration calculations.
A review of the nutrient recommendations for both elephant species was published by Sach et al. (2019). Although species-specific differences may be present in the physiology of African and Asian elephants, evidence-based findings on corresponding requirements for are lacking and further research is recommended (Bechert et al. 2019). Hence, based on the current knowledge we consider our recommendations to be valid for both elephant species kept in European facilities, and emphasize that the difference to other herbivores is much greater than that between the two elephant species.
Feed storage and preparation
As with all animal feed, appropriate storage conditions are essential to retain product quality, including appropriate insect and rodent control measures. All food storage must be designed in such a way to enable safe access by staff and limit wastage. A clear system for stock control and product traceability must be implemented.
Forage – must be protected from the weather (wet) and with good ventilation to prevent mould and degradation
Browse- must be protected from weather (wet) to prevent mould/degradation and consumption from other pest species
Pellets - purchased supplies should not exceed the amounts needed over a 4 to 6-month period to prevent degradation of vitamins, assuming ideal storage conditions. Most vitamins within pelleted feeds are stabilized for shelf life of up to 1 year – products must be individually checked and an inventory with record of expiry date, maintained within the animal feed store.
Produce – must be kept under refrigeration
1. Fresh grass paddocks
Ideally, access to grass paddocks should be provided to all elephants within the collection, although this may not be possible for some zoos due to space limitations, and in those with paddocks, not consistently throughout the year due to weather limitations. Paddocks must have appropriate drainage, especially around high use areas, such as gateways and feeding stations to maximise the amount of time in which they may be used by animals. A paddock management system must be in place for maintaining the paddock and preventing overgrazing. The time taken for elephants to consume small amounts of food via grazing is extremely important from a behavioural perspective and can assist in increasing the proportion of an elephant’s time spent foraging. For facilities without copious grass paddocks, implementation of a comprehensive feeding enrichment as a substitute is imperative. The latter may present an opportunity to compensate for limited space as recently reported by Scott and LaDue (2019).
2. Hay and fresh forages
Grass hay is an ideal forage source for species adapted to eating plants high in fibre.
It is important that the hay is of high hygienic quality, properly dried and cured. Hay should look green, and be free of weeds, insects, mould, twine, wire or any other foreign objects. Hay must be visually inspected before a delivery is accepted, and should be rejected if found to be substandard (mouldy, excessively dry and dusty, off-colour). During the process of unloading a delivery, this testing should continue, and not only be applied to the first few bales or batches that may have been deliberately chosen by the merchant to give a good impression.
Given that elephants should have hay available at all times, and that obesity rather than energy deficiency is the primary concern, the hay used should be of a low nutritional quality (e.g., crude protein 5-8%, neutral detergent fibre 60-70%, acid detergent fibre 40-50 % in dry matter). Ideally, the grass should have been cut at a very late growth stage, with long, lignified stems. Hay typically used for production animals, with cut at an earlier growth stage with soft, pliable stems and a high proportion of grass leaves, is not ideal for elephants due to its high energy content. Because hay suitable for elephants is typically not produced for the hay market, and because farmers cannot sell the same amount of hay if cutting their fields as late as reasonable for elephant hay compared to what they could sell cutting the same field several times, prospective contracting of farmers and fostering long-term relationships is recommended. Notably, local farming conditions, e.g. subsidies for an extensive land use with late cuts, will influence costs and practicalities.
Considering differences in the dietary needs of individual elephants (e.g. breeding vs. non-breeding females), it is recommended to have various badges of hay with differing energy content/digestibility on site. Differences in energy requirements should rather be met by different hay qualities than by the addition of other feedstuffs.
Hay of peculiar grass species, such as reeds, has been used successfully by some elephant facilities.
For the use of fresh forage, the same principles apply (grass of late maturity stage with long, lignified stems). If at all possible, the use of fresh forage should receive priority over dried forage, but will be necessarily limited to the non-winter season. Reedgrass or elephant grass, or other tall grasses, may be suitable. In theory, using whole maize plants without the cobs would also represent a suitable elephant feed. When feeding fresh forages, their dry matter content needs to be accounted for in ration calculation.
Browse is an essential dietary component, both nutritionally and from a behavioural perspective. It must be fed daily to all elephants throughout the year and may contain twigs, branches and stems up to entire tree logs. Consuming browse increases foraging time and has additional benefits for dental health. A plan must be in place for adequate browse provision throughout the year, including the winter months when leafy material is not available. Browse can be preserved for other species by silaging, freezing or drying, but for elephants, due to the volumes required, this is mostly not feasible. Rather, stems and twigs without leaves should be provided on a daily basis, as well as
evergreen species such as evergreen oak(Quercus ilex), bramble (Rubus fruticosus) or stinging nettle (Urtica spp.). Feeding conifers has proven successful for some collections. It may be logistically beneficial to additionally use branches that have been plucked clean of leaves and small twigs by other species of the same zoological institution for final consumption by the elephants, given that no hygienic concerns speak against this.
Straw can be a suitable low-caloric fibre addition to the diet of elephants and can be mixed in with the hay ration to prolong foraging time, especially in high feeding nets. Due to the high amount of forage required by elephants, mixing of hay and straw generally appears the less feasible option compared to the acquisition of long-stem grass hay of low nutritional (but high hygienic) quality. If mixing of hay and straw is done, the ratio should be determined in accordance with the dietary needs of the individual elephant. Like hay, straw must be of high hygienic quality, free of weeds, insects, mould, twine, wire or any other foreign objects and should be visually inspected before a delivery is accepted. Wheat or barley straw should be preferred, because oat straw typically contains a higher energy content.
The elephants’ requirements for bulky, low-energy roughage can be easily met with grass hay and straw, so that the more costly lucerne hay is typically not required. The feeding behaviour of elephants makes a loss of leafy material particularly likely when dealing with lucerne hay. Therefore, fresh lucerne or lucerne haylage would be considered more suitable due to the reduced leaf losses. Fresh lucerne or lucerne haylage might be used to increase the calorie and protein content of a specific animal’s diet under specific circumstances such as with geriatric animals or animals of compromised health. However, providing a grass hay of higher nutritional quality most likely is a more feasible solution.
For all forage items, gradual changes with a slow introduction of new material over the course of two weeks is recommended. In other words, the amount of the new diet item should be gradually increased so that only after one week, it represents 50% of the forage portion, and is given as the only forage only after the second week.
Other feed items
Except for special circumstances of particularly low forage quality or mishaps (e.g., sudden detection of forage spoilage due to roof leakage), there should be no need to provide elephants with pellets for maintenance energy requirements.
A variety of pelleted feedstuffs is available. Some are manufactured specifically for elephants and are designed to be fed in very small quantities, with forage making up most of the diet (hay, grass, browse, straw). These pellets provide high levels of vitamins, minerals and protein, in a concentrated form so only a small amount is required to meet the elephants’ nutritional needs. A combination of such a product with forages represents an easy and comparatively safe approach, because potential variation especially in the mineral composition of the forages is of little concern, given the baseline provision by the mineralized pellet. With this approach, the individual provision of specific amounts to each individual, according to its body mass, is prerogative.
It is advised that pellet selection is made by the zoo’s nutritionist or, if no nutritionist is on staff, by a nutritional consultancy service, which is sometimes also provided by renowned manufacturers.
To avoid digestive upsets, the introduction of any pellet into the diet should be gradual (increasing slowly over 2 weeks).
7. Fruits and vegetables (produce)
These should be fed in very limited amounts (less than 1 kg per elephant per day) and be documented as part of the daily diet ration. Produce is comparatively expensive, and amounts fed should not be required to contribute to vitamin and mineral provision. Even small quantities of higher sugar fruits, however, may significantly contribute to energy levels in the diet, adding to the risk of obesity. High sugar fruits should be replaced with vegetables – ideally leafy greens. In appropriate quantities, their use in training may be valuable. As it is easy to condition animals to the use of high-sugar items, but difficult to then reverse the conditioning, it appears prudent to refrain from the use of such items from the very beginning, and establish the use of leafy greens as training items.
This should be avoided – should this be required for the administration of medication, use must be monitored.
Elephants can be reluctant to consume unfamiliar foods- therefore it is appropriate to offer potential carriers for medication such as a bran mash periodically, so they will be consumed when needed. However, it should not be necessary to offer such items daily.
10. Vitamin and mineral supplements
The dietary concentrations of minerals and vitamins recommended for horses should in the most part be sufficient for elephants (Ullrey et al. 1997). Mineral deficiencies have rarely been reported and are best avoided through the adequate use of appropriate forages, supplemented with pelleted feed, rather than additional external supplementation where consumption is more challenging to ensure and monitor.
In specific situations such as an expected birth, the monitoring of serum calcium levels is recommended in order to avoid dystocia due to hypocalcemia (Hermes et al., 2008). Although the species-specific vitamin D and calcium metabolism in elephants is not fully understood so far (Childs-Sanford et al., 2020), efficacy of a dietary calcium supplementation has been reported (van Sonsbeek et al., 2013).
In particular when changing the diet of elephants, it may be appropriate to avoid eating those diet items (apples, bread) within their range of vision. In doing so, negative reactions by the elephants may be avoided.
Typically, it is recommended to analyse all feeds on a regular basis. However, the question each zoo has to ask itself is, how will that information be used. Analysing feeds appears mainly reasonable if there is a nutritionist on staff that makes use of that information. Yet, even with a nutritionist on staff, or the use of a consultancy service, it may be a more cost-efficient approach to design a diet based on forages and a concentrated pelleted food that covers a range of possible nutrient values of the forages, rather than adapting the pelleted component each time a batch of forage is analysed.
Having stated the potentially limited use of nutrient analyses, there is no excuse at all not to perform hygienic assessments of all feeds delivered to the zoo. Even if there is no nutritionist on staff, or even if there is no dedicated commissary manager, it cannot be excused if there is no personnel trained in evaluating the hygienic quality of forages, vegetables and pellets. In particular for forages, given their relevance and bulk in herbivore diets, personnel dedicated to evaluating and either accepting or rejecting a delivery, and dedicated to proper storage and assessment of storage quality, is indispensable.
It is commonly accepted that feeding in captivity must mimic feeding behaviour of wild counterparts. A variety of complex feeding opportunities to prolong foraging time throughout the day and night must be provided. Provision for food delivery in evening/early morning must be made when personnel is typically absent. With respect to the temporal occurrence of major sleep periods, no additional food should be presented between midnight and 6.00am to avoid sleep disturbance (Schiffmann et al. 2018b), which is evidently not difficult to achieve. Keepers must periodically monitor this via night-time video recording of all animals, to ensure all animals are able to obtain access to food and ensure feeding events do not encourage anticipatory or stereotypical behaviours.
Examples for daily ration quantities
Please note that the following daily rations serve as examples, making individual adaptation necessary before application. Ideally, a zoo should have a nutritionist on staff. If that is not the case, this task may fall to a veterinarian with some basic nutritional training, or can be outsourced – for a simple ration calculation – to a nutritional consultancy, of which there is a growing number in Europe. Alternatively, several manufacturers of zoo diets also provide nutritional consultancy. As with any business, the credibility of the service should be assessed, by asking for references from other zoos, and by plausibility checks. In particular, advice that appears to be tuned to use a maximum of pellets should be viewed with caution. Target overall diet composition (ingested roughage and non-roughage items) may be in the area of crude protein 10%, neutral detergent fibre 60%, acid detergent fibre 40 % in dry matter. Accurate calculation of the quantities required to cover the individual needs of an elephant would require constant analysis of the diet as well as monitoring roughage intake (by measuring offer and refusals) to allow estimation of the proportion of roughage and non-roughage diet items, which is impractical – all the more so if the recommendation of multiple feeding stations spread across the whole enclosure is heeded. Hence, continuous monitoring of an elephant’s physical condition by weighing and body condition scoring is strongly recommended (Schiffmann et al. 2019a). Subsequently diet composition and quantities can be adapted accordingly.
A Adult breeding female, body mass: 3´348kg, Body Condition Score (BCS): 5/10
Estimated daily dry matter intake [kg]: 3´348kg * 0.015 -> 50.22kg
B) Adult breeding male, body mass: 5´278kg, BCS: 7/10
Estimated daily dry matter intake [kg]: 5´278kg * 0.01 -> 52.78kg
C) Geriatric (non-breeding) female, body mass: 2´934kg, BCS: 4/10
Estimated daily dry matter intake [kg]: 2´934kg * 0.015 -> 44.01kg
D) Sub-adult male/female, body mass: 2´237kg, BCS: 8/10
Estimated daily dry matter intake [kg]: 2´237kg * 0.01 -> 22.37kg
Calculations based on the following parameters: maintenance requirement of daily dry matter intake 1-1.5% of an elephants body mass (Ullrey et al. 1997). Dry matter hay: 90% (Ullrey et al. 1997); recommended quantity pellets: elephant pellets, KasperFaunafood: 1kg/1´000kg BM per day.
Appropriate monitoring of body condition and weight is essential and should be conducted at least four times per year. Visual body condition scoring has been demonstrated as a practical and simple monitoring tool (Fernando et al. 2009; Schiffmann et al. 2018a; Chusyd et al. 2019) and is of peculiar importance if weighing is not feasible. Records must remain with the animal throughout its life and be recorded as appropriate e.g. via ZIMS. Consequences of obesity in captive elephants are extremely serious and will affect the animal’s long term captive health and welfare. There is strong evidence that obese animals are at increased risk of foot and joint lesions, altered metabolic markers and reduced reproductive success with increased labour length, dystocia, stillbirths and ultimately cow and calf death (Olson 2004; Freeman et al. 2009; Chusyd et al. 2018; Norkaew et al. 2018).
Where animals are not achieving an optimum Body Condition Score (BCS), a documented plan must be in place to achieve this with records kept of progress made. Daily, keepers must monitor diet consumption and report variations as appropriate. Individual diet plans must be made for each elephant and recorded.
Bax P, Sheldrick D (1963) Some preliminary observations on the food of elephant in the Tsavo Royal National Park (east) of Kenya. East African Wildlife Journal 1: 40-53
Bechert US, Brown JL, Dierenfeld ES, Ling PD, Molter CM, Schulte BA (2019) Zoo elephant research: contributions to conservation of captive and free-ranging species. International Zoo Yearbook 53: 1-27
Beekman JH, Prins H (1989) Feeding strategies of sedentary large herbivores in East Africa with emphasis on the African buffalo, Syncerus caffer. Journal of African Ecology 27: 129-147
Cerling TE, Harris JM, Leakey MG (1999) Browsing and grazing in elephants: the isotope record of modern and fossil proboscideans. Oecologia 120: 364-374
Childs-Sanford, S. E., Makowski, A. J., & Wakshlag, J. J. (2020). The vitamin D status of Asian elephants (Elephas maximus) managed in a Northern temperate climate. Journal of Zoo and Wildlife Medicine, 51, 1-12.
Chusyd DE, Brown JL, Hambly C, Johnson MS, Morfeld KA, Patki A, Speakman JR, Allison DB, Nagy TR (2018) Adiposity and reproductive cycling status in zoo African elephants. Obesity 26: 103-110
Chusyd DE, Brown JL, Golzarri-Arroyo L, Dickinson SL, Johnson MS, Allison DB, Nagy TR (2019) Fat mass compared to four body condition scoring systems in the Asian elephant (Elephas maximus). Zoo Biology:
Clauss M, Loehlein W, Kienzle E, Wiesner H (2003) Studies on feed digestibilities in captive Asian elephants (Elephas maximus). Journal of Animal Physiology and Animal Nutrition 87: 160-173
Clauss M, Steinmetz H, Eulenberger U, Ossent P, Zingg R, HummEl J, Hatt JM (2007). Observations on the length of the intestinal tract of African Loxodonta africana (Blumenbach 1797) and Asian elephants Elephas maximus (Linné 1735). Eur J Wildl Res (2007) 53: 68–72
Dougall H, Sheldrick D (1964) The chemical composition of a day´s diet of an elephant. Journal of African Ecology 2: 51-59
Fernando P, Janaka HK, Ekanayaka SKK, Nishantha HG, Pastorini J (2009) A simple method for assessing elephant body condition. Gajah 31: 29-31
Fowler ME, Mikota SK (2006) Biology, Medicine, and Surgery of Elephants. Blackwell Publishing, Iowa, USA
Freeman EW, Guagnano G, Olson D, Keele M, Brown JL (2009) Social factors influence ovarian acyclicity in captive African elephants (Loxodonta africana). Zoo Biology 28: 1-15
Hackenberger MK (1987) Diet digestibilities and ingesta transit times of captive Asian (Elephas maximus) and African elephants (Loxodonta africana), MSC Thesis University of Guelph, Guelph
Hatt JM, Clauss M (2006) Feeding Asian and African elephants Elephas maximus and Loxodonta africana in captivity. International Zoo Yearbook 40: 88-95.
Hermes, R., Saragusty, J., Schaftenaar, W., Göritz, F., Schmitt, D., & Hildebrandt, T. B. (2008). Obstetrics in elephants. Theriogenology, 70, 131-144.
Holdo RM, Dudley JP, McDowell LR (2002) Geophagy in the African elephant in relation to availability of dietary sodium Journal of Mammalogy 83: 652-664
Holdo RM, McDowell LR (2004) Termite mounds as nutrient-rich food patches for elephants. Biotropica 36: 231-239
Ilmberger N, Güllert S, Dannenberg J, Rabausch U, Torres J, Wemheuer B, Alawi M, Poehlein A, Chow J, Turaev D, Rattei T, Schmeisser C, Salomon J, Olsen PB, Daniel R, Grundhoff A, Borchert MS, Streit WR (2014) A comparative metagenome survey of the fecal microbiota of a breast- and a plant-fed Asian elephant reveals an unexpectedly high diversity of glycoside hydrolase family enzymes. PLoS ONE 9: e106707
Kabigumila J (1993) Feeding habits of elephants in Ngorongoro Crater, Tanzania. Journal of African Ecology 31: 156-164
Laws R (1970) Elephants and habitats in North Bunyoro Uganda. Journal of African Ecology 8: 163-180
Loehlein W, Kienzle E, Wiesner H, Clauss M (2003) Investigations on the use of chromium oxide as an inert, external marker in captive Asian elephants (Elephas maximus): passage and recovery rates. In: Fidgett A, Clauss M, Ganslosser U, Hatt JM, Nijboer J (eds) Zoo animal nutrition, vol 2. Filander, Fuerth, Germany
Norkaew T, Brown JL, Bansiddhi P, Somgird C, Thitaram C, Punyapornwithaya V, Punturee K, Vongchan P, Somboon N, Khonmee J (2018) Body condition and adrenal glucocorticoid activity affects metabolic marker and lipid profiles in captive female elephants in Thailand. PLoS ONE 13: e0204965
Olson D (2004) Elephant husbandry resource guide
Rees PA (1982) Gross assimilation efficiency and food passage time in the African elephant. African Journal of Ecology 20: 193-198
Sach F, Dierenfeld ES, Langley-Evans S, Watts M, Yon L (2019) African elephants (Loxodonta africana) as an example of a mega-herbivore making movement choices based on nutritional needs. PeerJ:
Schiffmann C, Clauss M, Fernando P, Pastorini J, Wendler P, Ertl N, Hatt JM (2018a) Body condition scores of European zoo elephants (Elephas maximus and Loxodonta africana): Status quo and influencing factors. Journal of Zoo and Aquarium Research 6: 91-103
Schiffmann C, Hoby S, Wenker C, Hard T, Scholz R, Clauss M, Hatt JM (2018b) When elephants fall asleep: A literature review on elephant rest with case studies on elephant falling bouts, and practical solutions for zoo elephants. Zoo Biology 38: 1-13
Schiffmann C, Clauss M, Hoby S, Hatt JM (2019a) Body Condition Scores (BCS) in European zoo elephants´ (Loxodonta africana and Elephas maximus) lifetimes - a longitudinal analysis. Journal of Zoo and Aquarium Research 7: 74-86
Schiffmann C, Hatt JM, Hoby S, Codron D, Clauss M (2019b) Elephant body mass cyclicity suggests effect of molar progression on chewing efficiency. Mammalian Biology 96: 81-86
Scott NL, LaDue CA (2019) The behavioral effects of exhibit size versus complexity in African elephants: A potential solution for smaller spaces. Zoo Biology:
Sukumar R (1990) Ecology of the Asian elephant in Southern India - II. Feeding habits and crop raiding patterns. Journal of Tropical Ecology 6: 33-53
Ullrey D, Crissey SD, Hintz H (1997) Elephants: nutrition and dietary husbandry. In: Allen M, Edwards M, Roocroft A (eds) Nutrition Advisory Group Handbook, pp 1-20
Van Sonsbeek, G. R., van der Kolk, J. H., van Leeuwen, J. P. T. M., Everts, H., Marais, J., & Schaftenaar, W. (2013). Effect of calcium and cholecalciferol supplementation on several parameters of calcium status in plasma and urine of captive Asian (Elephas maximus) and African elephants (Loxodonta africana). Journal of Zoo and Wildlife Medicine, 44, 529-540.
Wittemyer G (2011) Order Proboscidea. In: Wilson DE, Mittermeier RA (eds) Handbook of the Mammals of the World - Volume 2. Lynx Edicions, pp 50-79