Social behaviors within a group of captive female Hippopotamus amphibius

Behavior of Rio Sao Francisco Piranhas in Response to Changes in Space and Density

Previous observations of Rio Sao Francisco piranhas (Pygocentrus piraya) at Cleveland Metroparks Zoo revealed frequent aggressive interactions, which were associated with the injury and death of some individuals. Fishes are known to increase aggressive behavior when available space is limited. We compared the behavior of the piranhas longitudinally across three different space/density conditions: (1) in a group held in a small aquarium before the death of one individual, (2) in the same group after the death of one individual, (3) and in one individual of the group after it was later moved into a larger, multispecies aquarium. In the smaller aquarium, individuals maintained stable positions in the tank and remained inactive except to behave aggressively toward each other, retreat, or feed when food was offered. After the death of one individual, aggression decreased significantly but so did overall activity, including swimming behavior. After one individual was moved to a larger aquarium, it exhibited a striking increase in the amount of time spent swimming. Our data suggest that the well-being of P. piraya, and possibly other species of piranhas, might be better in large aquariums than in the small single-species exhibits often used in zoos and public aquariums. This study takes an important step in addressing the psychological and social well-being of bony fishes, an underrepresented area of research in zoos and aquariums.

Tusks, the extra-oral teeth

OBJECTIVE

The present review aims to: a) describe the features that support tusks in extra-oral position, and b) represent distinctive features of tusks, which provide insights into tusks adaptation to ambient conditions.

DESIGN

A comprehensive review of scientific literature relevant to tusks and comparable dental tissues was conducted.

RESULTS

The oral cavity provides a desirable condition which is conducive to tooth health. Therefore, it remains questionable how the bare (exposed) tusks resist the extra-oral conditions. The common features among tusked mammals indicate that the structural (e.g. the peculiar dentinal alignment), cellular (e.g. low or lack of cell populations in the tusk), hormonal (e.g. androgens), and behavioral traits have impact on a tusk's preservation and occurrence.

CONCLUSIONS

Understanding of bare mineralized structures, such as tusks and antlers, and their compatibility with different environments, can provide important insight into oral biology.

Sex Steroids as Regulators of Gestural Communication

Gestural communication is ubiquitous throughout the animal kingdom, occurring in species that range from humans to arthropods. Individuals produce gestural signals when their nervous system triggers the production of limb and body movement, which in turn functions to help mediate communication between or among individuals. Like many stereotyped motor patterns, the probability of a gestural display in a given social context can be modulated by sex steroid hormones. Here, we review how steroid hormones mediate the neural mechanisms that underly gestural communication in humans and nonhumans alike. This is a growing area of research, and thus we explore how sex steroids mediate brain areas involved in language production, social behavior, and motor performance. We also examine the way that sex steroids can regulate behavioral output by acting in the periphery via skeletal muscle. Altogether, we outline a new avenue of behavioral endocrinology research that aims to uncover the hormonal basis for one of the most common modes of communication among animals on Earth.

Activity and Pool Use in Relation to Temperature and Water Changes in Zoo Hippopotamuses (Hippopotamus amphibious)

Simple Summary

The following study examined the behaviors and water vs. land use of an outdoor exhibit by three zoo hippos. Behavioral observations were correlated with water temperatures at the exhibit, and compared to the number of days (0, 1, or 2 days) since the water within the outdoor pool had been dumped and refilled. The water changing of the pools had little effect on either the behaviors or pool use itself by the hippos. Water temperatures affected both the behaviors and pool use by the hippos, with warmer water temperatures being directly correlated with greater activity and overall pool use. The results suggest that temperature, rather than water change, was the more important factor in increasing overall pool use and general activity for the exhibited hippos.

Abstract

In the wild, hippopotamuses spend much of their daily activity in the water. In zoos, it is less clear the extent to which hippos spend time in the water. We examined how much time Woodland Park Zoo’s three hippos spent in their outdoor pool, based on: (a) temperature of the pool water, and (b) when the pool water was changed (approximately three times a week). Several digital temperature data loggers collected water and air temperature readings once every hour for six months. We correlated the water temperature readings with several behaviors the hippos could engage in, where the hippos were on exhibit (pool vs. land), and how many days it had been since a dump (0, 1, or 2 days). The results indicated that water changes had little effect on pool usage, while increasing water temperatures resulted in both increased activity and pool use. The results are discussed in terms of how these findings relate to wild hippo activity, current knowledge of zoo-housed hippo welfare, and future directions for zoo-housed hippo welfare and research.

Achieving optimal welfare for the Nile hippopotamus (Hippopotamus amphibius) in North American zoos and aquariums

Compared to other megafauna managed in zoos and aquariums, the current state of welfare for the Nile hippopotamus (Hippopotamus amphibius) is poorly understood. Complex behavior and physiological characteristics make hippos a difficult species to manage. Thus, hippos in managed care are currently at risk for a decreased state of welfare. In an effort to assess and improve conditions for this species, a survey was administered to North American institutions housing Nile hippos. This assessment utilized a multiple-choice format and consisted of questions relating to group structure, behavior, and exhibit design, allowing for the creation of cross-institutional, welfare-based analysis. Responses were gathered from 85.29% of the institutions to which the survey was distributed. Despite recommendations for maintaining groups of at least five individuals (Forthman, 1998), only 34.25% of hippos in North America were housed in groups of three or more. The survey also highlighted that 39.29% of institutions secure their hippos in holding areas overnight, despite their highly active nocturnal propensities. A better understanding of hippo behavior and environmental preferences can be used to inform wellness-oriented management practices to achieve a state of "optimal welfare".

Acoustic and behavioral repertoires of the hippopotamus (Hippopotamus amphibius)

This study describes the acoustic and behavioral repertoires of the common hippopotamus (Hippopotamus amphibius). Simultaneous audio and video recordings were collected of male and female hippos at Disney's Animal Kingdom(®). Visual inspection of spectrograms resulted in classifying signals into three main categories (burst of air, tonal, and pulsed) produced in-air, underwater, or simultaneously in both mediums. Of the total acoustic signals, most were produced underwater (80%), and the majority of the total signals were tonal (54%). Using multivariate analysis of the acoustic parameters, 11 signal types were described and differentiated. In the burst of air category, chuffs and snorts were distinguished by minimum and peak frequency, and bubble displays were described. In the tonal category, grunts, groans, screams, and whines were distinguished by several frequency measures (e.g., minimum, maximum, fundamental, peak frequency). Wheeze honks were tonal signals that often involved a chorus of overlapping calls. In the pulsed category, click trains, croaks, and growls were distinguished by frequency and duration. Video analysis demonstrated that chuffs, groans, and whines were associated with submissive contexts, while snorts, grunts, and growls were associated with dominance contexts. These results provide further information about the acoustic signals and concurrent behavior of hippos.

Female nile hippopotamus (Hippopotamus amphibius) space use in a naturalistic exhibit

Zoological institutions provide naturalistic exhibits for their animals in order to offer a more appealing look for visitors and give the animal the opportunity to engage in more natural behaviors. Examining space use of the animals in the naturalistic exhibit may aid in the management of these animals and inform future naturalistic exhibit design. The hippopotamus is an amphibious ungulate that spends much of its days in the wild in the water but may be found along the banks of the rivers basking in the sun. Our objective was to determine how captive female hippos utilize their exhibit by examining whether hippos selected for certain areas of a naturalistic exhibit. Scan sample data were collected on a group of nine captive female hippos housed at Disney's Animal Kingdom®. Using ArcView, the data were analyzed to determine distribution of hippos in the exhibit and their utilization of depth categories while in the water. Hippos were found to aggregate in preferred areas of the exhibit, mostly water, and selected most for water depths of 0.6-1.0 m. These results will aid in the understanding of hippopotamus space use and may aid zoological institutions in the design of naturalistic exhibits for hippos.