Greater One Horned Rhinoceros

Behavior

Ranging Behavior and Sociality

Asian rhinoceros species are the most solitary of the extant rhino species (Ripley, 1952; Hutchins and Kreger, 2006), but temporary groups of subadults might be observed in the wild (Fouraker and Wagener, 1996). Greater one-horned rhinos also have the greatest affinity for water (Hutchins and Kreger, 2006). Wild greater one-horned rhinos feed on grasses in moist, riverine forest and khair-sissoo forest during the cooler season, and in tallgrass floodplain during the hot season (Steinheim et al., 2005). Both in the wild and in managed settings, male and female rhinos defecate almost exclusively at dung piles (88% of the time; Laurie, 1982). Home range boundaries are delineated by scent marks left by males during spray-urination (Ripley, 1952), dung-kicking, scraping with the fore- and/or hindlegs, and horn-scraping (Table 4.26; Owen-Smith, 1988). Home ranges of males overlap, therefore males must defend estrous females from other males." (Laurie, 1982)

Reproductive Behavior

It is recommended that males and females of this species should be kept separately and introduced only for breeding purposes (Fouraker and Wagener, 1996). While the most common vocalizations are “grunts” or “low bellows” (Table 4.26), females will use a high, penetrating, whistling vocalization to communicate their sexual receptivity (Ripley, 1952) (and their location in the wild) beginning six to ten hours before breeding (Hutchins and Kreger, 2006). This can attract more than one male in the wild, leading to violent male-male interactions (Laurie, 1982). Precopulatory behavior in this species also can be aggressive, including chasing up to 2 km (1.2 mi) and biting by both sexes (Hutchins and Kreger, 2006). Laurie (1982) suggested that this behavior might guarantee that a female mates with the most dominant male in the vicinity, and females will avoid undesirable males by running away or fighting when cornered (Hutchins and Kreger, 2006). As the female rhino approaches peak estrus, indicated by behaviors such as increased urine spraying, inappetance, increased vocalizations and vulva winking (Table 4.27), an introduction should be attempted.

It has been noted that peak estrus lasts approximately 24 hours, and optimal conception chances occur between hours eight and 12 (Fouraker and Wagener, 1996). Eventually, preliminary mounts will be tolerated until the female eventually stands with her tail curled for full penetration (Fouraker and Wagener, 1996). Greater one-horned rhinos generally have been reported to mount before an erection occurs (Fouraker, and Wagener 1996). At full copulation, rhinos may remain coupled for 30 minutes to one hour, with ejaculations every few minutes (Fouraker and Wagener, 1996). It is a good idea to keep a record of all observations of sexual behavior, and suggested instructions for doing so, as well as a data sheet, are provided in Appendices E and G, respectively. Cows will become aggressive to their older calves approximately one week prior to the birth of the next calf (Laurie, 1982), but termination of the relationship ranges from gradual to immediate (Hutchins and Kreger, 2006).

Prior to parturition, zoo-managed female greater one-horned rhinos might pace within the enclosure (Hutchins and Kreger, 2006). Parturition usually lasts ten to 12 hours from water-break, though first-time mothers may take longer to clave (Fouraker and Wagener, 1996). Infants may nurse hourly while older calves nurse approximately every couple of hours (Fouraker and Wagener, 1996). It has been reported that as the calf ages, nursing will usually decrease in frequency (Fouraker and Wagener, 1996). Young calves under two months of age may be left alone while their mother moves up to 800 m (2,625 ft) away to forage, but they remain close to their mother when older than two months (Laurie, 1982). If the facility is able to house multiple female greater one-horned rhinos together, the cow and calf should not be introduced to the others for approximately four months following birth (Fouraker and Wagener, 1996).

A common behavioral abnormality observed in captive rhinos is excessive horn rubbing (Hutchins and Kreger, 2006), which might indicate boredom or distress.

Table 4.26. Ethogram to assist with general rhino management (adapted from Fouraker and Wagener

Behavior During Introductions (Fouraker and Wagener, 1996)

Male and female greater one-horned rhinos should be introduced only during the female’s estrous period. Introductions often result in aggression, and it should be noted that rhinos of both sexes have been the aggressors. Behaviors that have been noted during rhino introductions are listed in Table 4.28. Territorial defense is often limited to ritualized confrontations, in which two rhinos advance toward each other but stop and engage in a horn-to-horn stare (Tables 4.26 and 4.28). Also as part of this ritual, the two individuals may touch horns, back apart, and wipe their horns on the ground (Nowak, 1991). More intensive conflicts (Table 4.29) involve charges and the infliction of injuries by horning or ramming. It is important to note that what is often perceived as serious or dangerous aggression between rhinos is, in fact, normal behavior requiring no intervention of any kind. Along with increased size and thick skin comes decreased vulnerability compared with many other animals. In some cases, aggression may proceed to a point at which management should intervene to prevent serious injury. Captive managers should allow some aggression during an introduction but be prepared to intervene in the event that aggression threatens the lives of one or more rhinos.

Guidelines for intervening may vary across institutions, but in general, careful consideration should be given to intervening in an introduction before aggression reaches Level 5 (Table 4.29). Stopping an introduction at a level prior to this will not lessen aggression during a subsequent introduction attempt. Animals that are allowed to “settle their differences” will establish some territorial boundaries and will usually not engage in serious aggression again, with the exception of a male attempting to approach an estrous female. In sum, moderate aggression is commonplace in any rhino introduction; sparring and fighting will occur and result in minor injuries (cutaneous wounds). However, in most cases, aggression levels prior to Level 5 may be allowed to continue using the discretion of management.

Animal personality and disposition should always be considered in introductions. A subordinate animal should be introduced to a more dominant animal in an enclosure familiar to the subordinate. In the case of multiple-animal introductions, the most subordinate animal should be introduced to the next most subordinate, and so on up the dominance hierarchy. Greater aggression may be noted in some individuals in the presence of an estrous female, therefore, any introduction attempt at this time should be especially well-monitored. Aggression may be meaningfully reduced by allowing individuals to become familiar with each other through protected contact (e.g., through enclosure bars) or, possibly, by exposing them to one another’s odors for a period prior to introduction.

In order to conduct appropriate behavioral studies, many institutions have utilized ZooMonitor.

ZooMonitor is an app developed by Lincoln Park Zoo that allows you to record animal behavioral data, visualize the information, and export the data for analysis. When designing ZooMonitor, the goal was to make it easy for experts and non-experts alike to collect data that will aid in making and evaluating management decisions that impact animal welfare.
ZooMonitor was made possible in part by the Institute of Museum and Library Services MG-30-14-0045-14, and is free to download for qualifying institutions.