Behavioural responses of captive hippopotamus(hippopotamus amphibius)in lactation season:Maternal investment and plasticity of infant self-independence

In order to promote hippopotamus management in the captive and ex-situ environment, especially the control of behavioural and physiological status during breeding and lactation seasons, we conducted a preliminary study on behavioural responses of a pair of hippos including both mother and infant in Hangzhou Wildlife Park, China. The study of the captive hippos for about 1-month in the lactation season was carried out during August and September, 2009. The behavioural patterns were identified by all occurrence sampling and instantaneous scanning sampling methods with 5-10 min intervals. As a result, mother-offspring conflicts and interactions did occur throughout the whole study period. Early maternal investment showed a positive trend in activity rhythms (slope = 0.0014, Z = 0.3027, P ＜0.001) and a negative trend (slope = -0.0066, Z = 0.8807, P＜0.001) in territorial occupation of water, all of which supported our hypotheses that the mother hippo might exert less care for the infant and cut down on her own obligations in nursing. For infant self-independence, during the whole lactation season, the primary trends of activities and territorial occupation dynamics of the infant hippo were slightly different from before, judging from linear models (slope = -0.0017, Z = 0. 3309, P＜0.001). However, the frequencies of activities were not stable, especially at around 12 days of age. The trends of territorial occupation (slope = -0.0071, Z= 0. 904, P＜0.001) also showed negative dynamics in water body occupation by the time the infant hippo grew up. The general trend (slope = -0.005, Z = 0.06, P＜0.001) of suckling dynamics was demonstrably negative, with an upwards fluctuation at period 3 (10-15th day). This also illustrated that as the infant developed, the dependency on the mother was reduced at the end of the lactation season. In addition, a sharp decline between P3 and P4 also supported the mother-offspring conflict theory. In general, time budgets of hippos in active behaviour were (31.8±2.1)% for the mother and (32.1 ±2.6)% for the infant. Spatial distributions in water within temporal limitations were (80.1 ±2.7)% for the mother and (81.8±2.7)% for the infant. Behavioural dynamics showed strong synchronous relations between maternal investment and infant independence. Our current short-term investigation proves to be a key in management and conservation of hippopotami during the lactation season.     

Activity patterns at the Arctic Circle: nocturnal eagle owls and interspecific interactions during continuous midsummer daylight

Circadian rhythms result from adaptations to biotic and abiotic environmental conditions that cycle through the day, such as light, temperature, or temporal overlap between interacting species. At high latitudes, close to or beyond the polar circles, uninterrupted midsummer daylight may pose a challenge to the circadian rhythms of otherwise nocturnal species, such as eagle owls Bubo bubo. By non‐invasive field methods, we studied eagle owl activity in light of their interactions with their main prey the water vole Arvicola amphibius, and their competitor the white‐tailed eagle Haliaeetus albicilla during continuous midsummer daylight on open, treeless islands in coastal northern Norway. We evaluated circadian rhythms, temporal overlap, exposure, and spatial distribution. The owls maintained a nocturnal activity pattern, possibly because slightly dimmer light around midnight offered favourable hunting conditions. The eagles were active throughout the 24‐h period as opposed to the strictly diurnal rhythm reported elsewhere, thus increasing temporal overlap and the potential for interference competition between the two avian predators. This may indicate an asymmetry, with the owls facing the highest cost of interference competition. The presence of eagles combined with constant daylight in this open landscape may make the owls vulnerable to interspecific aggression, and contrary to the available literature, eagle owls rarely exposed themselves visually during territorial calls, possibly to avoid detection by eagles. We found indications of spatial segregation between owls and eagles reflecting differences in main prey, possibly in combination with habitat‐mediated avoidance. Eagle owl vocal activity peaked in the evening before a nocturnal peak in visual observations, when owls were active hunting, consistent with the hypothesis of a dusk chorus in nocturnal bird species. The owls may have had to trade‐off between calling and foraging during the few hours around midnight when slightly dimmer light reduced the detection risk while also providing better hunting conditions     

Entodiniomorph Ciliates from the Stomach of Hippopotamus amphibius, with Descriptions of Two New Genera and Three New Species

Entodiniomorph ciliates, belonging to the family Cycloposthiidae, are described from the stomach contents of Hippopotamus amphibius. Monoposthium acanthum gen. n., sp. n., with typical cycloposthiid structure, differs from other genera in having only 1 caudalium. Parentodinium gen. n., represented by P. africanum sp. n. and P. ostrea sp. n., although superficially resembling Entodinium, is considered to be a relatively unspecialized cycloposthiid.     

Colonisation dynamics during range expansion is poorly predicted by dispersal in the core range

The potential ranges of many species are shifting due to changing ecological conditions. Where populations become patchy towards the range edge, the realised distribution emerges from colonisation–persistence dynamics. Therefore, a greater understanding of the drivers of these processes, and the spatial scales over which they operate, presents an opportunity to improve predictions of species range expansion under environmental change. Species reintroductions offer an ideal opportunity to investigate the drivers and spatial scale of colonisation dynamics at the range edge. To this effect, we performed and monitored experimental translocations of water voles to quantify how colonisation and local persistence were influenced by habitat quality and occupancy. We used a novel statistical method to simultaneously consider effects across a range of spatial scales. Densely occupied neighbourhoods were highly persistent and frequently colonised. Persistence was more likely in high quality habitat, whereas the influence of habitat quality on colonisation was less clear. Colonisation of suitable habitat in distant, sparsely occupied areas was much less frequent than expected from the well documented high dispersal ability of the species. Persistence of these distant populations was also low, which we attribute to the absence of a rescue effect in sparsely populated neighbourhoods. Our results illustrate a mismatch between the spatial scales of colonisation dynamics in the core and edge of a species’ range, suggesting that recolonisation dynamics in established populations may be a poor predictor of colonisation dynamics at the range edge. Such a mismatch leads to predictions of long lags between the emergence and colonisation of new habitat, with detrimental consequences for a species’ realised distribution, conservation status and contribution to ecosystem function. Conservation translocations that also reinforce existing populations at the range edge might stimulate the rescue effect and mitigate lags in expansion.     

Cooling and freezing of epididymal sperm in the common hippopotamus (Hippopotamus amphibius)

Knowledge concerning reproduction in common hippopotamus is scarce and in particular very little is known about male reproductive physiology and sperm cryopreservation. Testes were obtained from nine castrated bulls and sperm extracted from the epididymides of eight of these individuals. Mean ± SEM values of reproductive parameters were: testicular weight (including epididymis and tunicas)—275.9 ± 54.1 g, total sperm motility—88.1 ± 4.2%, total cells extracted—11.0 ± 3.6 × 10⁹, intact acrosome—87.7 ± 1.8%, intact sperm morphology—51.6 ± 4.1%, and, for 3 individuals, hypoosmotic swelling test for membrane integrity—83.3 ± 1.8%. Chilled storage extenders tested were Berliner Cryomedium (BC), Biladyl^®, modification of Kenney modified Tyrode's medium (KMT), and Human Sperm Refrigeration Medium (HSRM). Extender had significant effect on post-dilution motility and motility and intact morphology after 4h and 24h at 4°C (P ≤ 0.007 for all). Berliner Cryomedium and HSRM were superior to Biladyl^® and KMT. Freezing extenders tested were BC with either 6% dimethyl sulfoxide (Me₂SO), or 5%, 7%, or 10% glycerol. Post-thaw motility was < 5% in 3/7 bulls in all extenders. When frozen in BC with 6% Me₂SO, one bull had 15% post-thaw motility and 3/7 had 20 to 60%. In glycerol, 3/7 had 15-30% post-thaw motility in 5%, 2/7 in 7%, and 1/7 in 10%. The extender had significant effect on post-chilling motility (P = 0.008), post-thaw morphology (P = 0.016), and motility 30 min after thawing (P = 0.015). Berliner Cryomedium with 6% Me₂SO or 7% glycerol were the freezing extenders of choice. Information obtained in this study allows initiation of cryobanking of sperm from the common hippopotamus which is of particular importance for genetically valuable individuals.     

Genetic structure,ecological versatility,and skull shape differentiation in Arvicola water voles (Rodentia,Cricetidae)

Water voles from the genus Arvicola display an amazing ecological versatility, with aquatic and fossorial populations. The Southern water vole (Arvicola sapidus) is largely accepted as a valid species, as well as the newly described Arvicola persicus. In contrast, the taxonomic status and evolutionary relationships within Arvicola amphibiussensu lato had caused a long-standing debate. The phylogenetic relationships among Arvicola were reconstructed using the mitochondrial cytochrome b gene. Four lineages within A. amphibiuss.l. were identified with good support: Western European, Eurasiatic, Italian, and Turkish lineages. Fossorial and aquatic forms were found together in all well-sampled lineages, evidencing that ecotypes do not correspond to distinct species. However, the Western European lineage mostly includes fossorial forms whereas the Eurasiatic lineage tends to include mostly aquatic forms. A morphometric analysis of skull shape evidenced a convergence of aquatic forms of the Eurasiatic lineage toward the typically aquatic shape of A. sapidus. The fossorial form of the Western European lineage, in contrast, displayed morphological adaptation to tooth-digging behavior, with expanded zygomatic arches and proodont incisors. Fossorial Eurasiatic forms displayed intermediate morphologies. This suggests a plastic component of skull shape variation, combined with a genetic component selected by the dominant ecology in each lineage. Integrating genetic distances and other biological data suggest that the Italian lineage may correspond to an incipient species (Arvicola italicus). The three other lineages most probably correspond to phylogeographic variations of a single species (A. amphibius), encompassing the former A. amphibius, Arvicola terrestris, Arvicola scherman, and Arvicola monticola.     

Surgical castration of the male common hippopotamus (Hippopotamus amphibius)

In a prospective, clinical, surgery study we report here for the first time, in detail, on the surgical castration of 10 captive adult male common hippopotami (Hippopotamus amphibius). The successful procedures, a species-specific modification of standard equine castration techniques, provide valuable insight into the spatially dynamic nature of the common hippopotamus testis. The use of ultrasonography to locate the testis before and during the procedures and species-specific positioning during surgery greatly facilitated this distinctive procedure. Additionally, this surgical method provides an important additional tool for captive management of the common hippopotamus. Castration of individual males not only facilitates population control but can potentially also be employed to limit intermale aggression.     

Evolution of ontogeny in the hippopotamus skull: using allometry to dissect developmental change

Allometry describes the effect of size change on aspects of an organism's form and can be used to summarize the developmental history of growing parts of an animal. By comparing how allometric growth differs between species, it is possible to reveal differences in their pathways of development. The ability to compare and categorize developmental change between species is demonstrated here using morphometric methods. This involves the interspecific statistical comparison of a large number of bivariate relationships that summarize ontogenetic trajectories. These linear ontogenetic trajectories can be modified as they evolve in any of three ways: ontogenetic scaling indicative of change in the duration of growth, lateral shifts indicative of changes in prenatal development, and directional change indicative of novel modes of postnatal growth. I apply this analysis to skulls of the common hippopotamus ( Hippopotamus amphibius ) and the pygmy hippopotamus ( Hexaprotodon liberiensis ). The number of allometric changes falling into each category was statistically determined and Jolicoeur's multivariate generalization of simple allometry was used to provide an overview of cranial variation. For these skulls, directional change was not found to be statistically significant, but ontogenetic scaling and lateral shifts were both common. This indicates that conserved patterns of growth covariance (ontogenetic scaling) can be separated from novel or derived patterns (directional change and/or lateral shifts). This study demonstrates that He. liberiensis is not simply an ontogenetically scaled version of its larger relative. The evolutionary implications of allometric growth variation are discussed in the light of these findings and those of other studies.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 625–638.     

Tawny owl prey remains indicate differences in the dynamics of coastal and inland vole populations in southern Finland

Some studies suggest that mild winters decrease overwinter survival of small mammals or coincide with decreased cyclicity in vole numbers, whereas other studies suggest non-significant or positive relationships between mild winter conditions and vole population dynamics. We expect for the number of voles to be higher in the rich and low-lying habitats of the coastal areas than in the less fertile areas inland. We assume that this geographical difference in vole abundances is diminished by mild winters especially in low-lying habitats. We examine these relationships by generalized linear mixed models using prey remains of breeding tawny owls Strix aluco as a proxy for the abundance of voles. The higher number of small voles in the coastal area than in the inland area suggest that vole populations were denser in the coastal area. Vole populations of both areas were affected by winter weather conditions particularly in March, but these relationships differed between areas. The mild ends of winter with frequent fluctuations of the ambient temperature around the freezing point (“frost seesaw”) constrained significantly the coastal vole populations, while deep snow cover, in general after hard winters, was followed by significantly lowered number of voles only in the inland populations. Our results suggest that coastal vole populations are more vulnerable to mild winters than inland ones. We also show that tawny owl prey remains can be used in a meaningful way to study vole population dynamics.     

Répartition des Hippopotamidae(Mammalia,Artiodactyla) en Europe occidentale implications stratigraphiques et paléoécologiques

The present note is intended to disparage a certain number of groundless but commonly accepted assertions concerning the quaternary Hippopotamidae of Western Europe.The remains of European quaternary hippopotamusare not as rare as it is generally believed: more than 270 localities prove it. The most important sites are described here.The quaternary European hippopotamus do notnecessarily characterise an «interglacial age and, besides, even though some of them belong to the Cromerian or to the Eemian, some other belong to colder periods, from the beginning of the middle Pleistocene until the end of the ancient Würm. The paleoecological implications compel us to moderate the value of hippopotamus remains considered as paleoclimatic indicators, in any case as far as temperature is concerned.