Behaviour/Feeding ecology


Matthias Lechner-Doll Dr.1
1 Institute for Zoo Biology and Wildlife Research, P.O. Box, 10315 Berlin, Germany

The aim to ensure an adequate nutritional basis for wild herbivores in captivity is difficult to realize in many cases, mainly because of insufficient data on the particular needs of the species. The natural diet is usually impossible to offer, in particular for selective herbivores and for animal species away from their natural climatic zone. To adapt commercial dietary components designed for domestic livestock may be the only alternative in most cases. However, in temperate climatic zones and close to the polar regions, seasonal variations of the biomass available for consumption of wild ungulates varies several orders of magnitude, both in respect to quantity and to quality. This is mainly a result of the short vegetation period. Wild ungulates in the polar region (but also in temperate zones) consequently are strictly seasonal. Reproductive functions with the highest nutritional demand (late pregnancy and lactation in particular) must be synchronized with the vegetation period. However nutritional strategies are often very different between species. Examples for different ungulate species and feeding types will be discussed. Energy expenditure is greatly reduced in winter in many northern cervids, energy balance is negative in winter and body fat reserves may contribute substantially to winter energy expenditure. Voluntary feed intake and the extend to which body reserves are accumulated during the vegetation period are not only a matter of feed quality and quantity offered, but depend on day length and season. Seasonality of feeding behavior changes seem to be inherited and thus remain present in captivity, even if continuous feed supply is guarantied since many generations. As a consequence for practical management, northern cervids in particular may need to be fed below voluntary consumption in autumn to avoid the accumulation of body reserves, which are not utilized during winter in captivity. A second possible management strategy may use the natural seasonal rhythm. To simulate winter conditions animals may be fed below maintenance and may thereby reduce excess body reserves accumulated previously.


Thomas Lutz Dr.1
1 Institute of Veterinary Physiology, University of Zuerich, Winterthurerstrasse 260, 8057 Zuerich, Switzerland

Adult individuals are usually characterized by a balance between energy intake and energy expenditure. Food intake is controlled by various feed back loops. Short-term and long-term regulatory systems can be differentiated. The feed back signals are integrated in the central nervous system (CNS) and translated into an appropriate feeding response. Short-term regulation of food intake mainly involves feed back signals originating in the gastrointestinal (GI) tract. They may be positive (e.g. from the oral cavity) or negative in nature. Distension of the stomach (or the forestomachs in ruminants) leads to the activation of vagal afferents projecting to the nucleus of the solitary tract (NTS) in the hindbrain being connected with the hypothalamus. The presence of nutrients in the small intestine (or rumen in ruminants) is sensed and the information transmitted via vagal afferents or via the release of GI hormones, e.g. cholecystokinin (CCK). Besides CCK, other hormones (e.g. gastrin-releasing peptide and the pancreatic hormones amylin, glucagon and insulin) also play an important role in the regulation of food intake. These satiety hormones act partly via receptors on vagal or splanchnic afferent nerves (CCK) whereas amylin and insulin appear to act directly in the CNS. Feed back signals from the hepatoportal area are postabsorptive in nature. The availability of glucose (propionate in ruminants), the oxidation of fatty acids and the energy status in general appear to be sensed in the hepatoportal area with the signals being transmitted mainly via hepatic vagal afferents. The lipostatic theory of the long term regulation of food intake and body weight postulates the presence of humoral factors whose concentration depends on the size of the adipose tissue. The most important signals are leptin and insulin whose plasma concentrations increase with the degree of obesity. Both constitute negative feed back signals acting directly on the brain, their main target organ being the hypothalamus, the main integrating center for the control of food intake. Within the CNS, a plethora of substances interact in a complex system to control food intake. Among them are the neurotransmitters serotonine, histamine, norepinephrine and dopamine and the neuropeptides corticotropin releasing factor (CRF)/melanocortin (MC) and neuropeptide Y (NPY). The anorectic effects of leptin and insulin, e.g., also appear to be mediated via the NPY and CRF/MC systems.


Alfred Melissen Dr.1
1 Otterpark AQUALUTRA, De Groene Ster 2, 8926 XE Leeuwarden, The Netherlands

As Eurasian otters are kept in many countries in Europe, with very different climatological circumstances during the year, it is difficult to advise on food quantities that have to be given to an individual. In this report temperature related energy intake data are presented as a guideline. Otters are large consumers, daily food intake can mount up to 15% bodyweight in wintertime, or up to 20% bodyweight during lactation. In order to investigate variation in energy intake related to changing seasons and lactation the food intake of 4 otters kept at the Otter park AQUALUTRA was monitored. All animals were fed an identical diet, consisting on 2/3 of gross energy intake provided by mackerel and 1/3 of gross energy intake from one-day-old chickens. During the test period all animals appeared healthy and were behaving normally. Two adult, non-pregnant or lactating animals (1.1) of average bodyweight housed in the public accessible enclosures were followed during one year. The animals were fed three times daily ad lib to the point they would not appear from their nest boxes for their last feeding time, then the daily quantity of food given was reduced. When the animals became too aggressive to the keepers because of hunger, the quantity of food offered was increased. Together with this data on average temperature during the test period were collected, in order to be able to give more specific advise on gross energy intake related to average environment temperature. Furthermore the effects of lactation on energy intake were studied in two females otters. They were housed in the breeding center and fed the same diet, the quantities of food offered being determined by the animals in the public enclosures. The animals were fed once daily at the end of the day, the amount was titrated by the aggressiveness of the animals during feeding time and the amount of food not eaten the next morning. Both females were housed under comparable conditions in adjacent enclosures, and were monitored over a period of six months. One of the females was mated, became pregnant and raised three cubs successfully. The other female, of approximately the same bodyweight, remained unmated and was used as reference animal to eliminate climatological effects. Results indicate that in winter the amount of food offered should be monitored carefully (weighing the amount given and the amount not-eaten daily!) and increased in our case up to almost 200% compared to the lowest summer averaged week intake. For lactating females the amount increases even more (up to almost 300%). Regarding the fact that an important component of otter diets (fish) is very perishable, husbandry measures are necessary in order to provide the animals a sufficient amount of proper food.


Udo Ganslosser PD Dr. 1 and David B. Croft 2
1 Institute of Zoology, University of Erlangen, Staudtstrasse 5, 91058 Erlangen, Germany, 2 School of Biological Sciences, University of New South Wales, Sidney, NSW 2052, Australia

Macropodoids posses morpho-physiological as well as ecological adaptations similar to herbivorous placentals e.g. ungulates. Both from the morphology of dentition and jaw mechanics and from morphophysiology of stomach and gut function, at least three types of macropodids can be distinguished: browsers, intermediate feeders, and grazers. Within the potoroids (rat-kangaroos), a fourth group, the frugivores and subterraneous bulb-feeders can be found. Kangaroos and their relatives are ideally suited for studies of sex and size differences in feeding ecology, and possible influences of behavioural as well as morphological constraints acting on them. One reason for this is that most of the medium to large-sized species are heavily sexually dimorphic in size, with males growing throughout their lives. This allows an intraspecific comparison of food selection, habitat choice and foraging behaviour not only between sexes but also between age classes and, in case of females (pouch size as an indicator!), reproductive conditions. Influences of food quality and food availability on selectivity and time budgets were studied for several species of macropods, and possible consequences on social as well as reproductive behaviour will be discussed and related to captive management.


Mike Jordan 1
1 Animal Management Section, Sparsholt College Hampshire, Sparsholt, Hants SO21 4 NK, United Kingdom

Of all the Mammalian Orders, the Order Rodentia contains the largest number of mammal species. The Rodents comprise a total of 2021 species, which represents 43.7% of all mammals. They occupy all six zoogeographical regions of the world, and in each region different species have evolved to occupy a massive diversity of ecological niches. This ranges from commensal species such as the Western House Mouse (Mus domesticus) to tropical arboreal species such as Prevost's Squirrel (Callosciurus prevosti). In behaviour the rodents are again incredibly diverse and species exist that can provide examples of many different strategies across a wide range of habitats. Rodents show a wide variety of foraging specialisations, since by developing such specialist foraging behaviours each species fully exploits its habitat and reduces competition with other inhabitants of the same area. However, within a large number of zoological collections the diversity of rodents is poorly known and even more poorly displayed. Despite the large variety in natural diets and foraging ecology amongst rodents, most species are still fed in captivity with exactly the same diet and food presentation techniques irrespective of their wild ecology. For the majority of rodents this consists of a seed mixture fed in a static food bowl. Rodents have the potential to be more effectively displayed if their natural foraging behaviours are utilised, as well as enhancing the welfare of the individuals themselves through providing environmental enrichment. An example of this is the Fattailed Duprasi (Pachyuromys duprasi). In the wild this animal is a voracious hunter, and given a regular supply of live insects and molluscs can display active hunting behaviour. Zoos must therefore look to what happens in the wild in order to enhance their displays and improve welfare - and rodents should not be exempt from this rule.