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Blood pressure and flow rate in the giraffe jugular vein

Experimental measurements in the jugular veins of upright giraffes have shown that the internal pressure is somewhat above atmospheric and increases with height above the heart. A simple model of steady viscous flow in an inverted U-tube shows that these observations are inconsistent with a model in which the blood vessels in the head and neck are effectively rigid and the system resembles a siphon. Instead, the observations indicate that the veins are collapsed and have a high resistance to

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The role of water abundance, thermoregulation, perceived predation risk and interference competition in water access by African herbivores

In African savannas, surface water can become limiting and an understanding of how animals address the trade-offs between different constraints to access this resource is needed. Here, we describe water access by ten African herbivore species in Hwange National Park, Zimbabwe, and we explore four possible determinants of the observed behaviours: water abundance, thermoregulation, perceived predation risk and interference competition. On average, herbivores were observed to drink in 80% of visits to a waterhole. The probability of drinking was higher

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Densities of mammals in partially protected areas: the Katavi ecosystem of western Tanzania

In Africa the majority of conservation areas sanction some sort of human activities within their borders but few of them are part of community‐based conservation schemes. The effectiveness of these state‐owned, partially protected areas in conserving mammalian fauna is largely unknown. Large and medium‐sized mammal densities in three different sorts of partially protected area were compared to mammal densities in an adjacent national park in western Tanzania by driving 2953 km of strip transects over a 14‐month period. In a Game

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Giraffes (Giraffa camelopardalis peralta) of Niger

Thirty years ago giraffes were found all over the Sudano-Sahelian area, from Mauritania to Chad. Over the last 20 years, due to loss of habitat and poaching, giraffe populations have decreased. In Niger large herds were present in the Tanout area, between Agadez and Zinder, but they disappeared because of recurring drought. During the eighties, giraffes were present in the Ayorou area, but suddenly disappeared because of poaching along the Malian border and the 1984 drought. Today the sub-species Giraffa

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The structure of the masseter muscle in the giraffe (Giraffa camelopardalis)

In the giraffe (Giraffa camelopardalis), the masseter muscle was divided into several layers. The superficial and more medial (second) tendinous sheets of the masseter muscle fused with each other at the dorso-caudal part and a fleshy portion was located between these tendinous sheets. In the rostral part, the most superficial tendinous sheet turned around as a compact tendon and attached to the facial crest (Crista facialis). The turned tendinous sheet, however, never fused with the second tendinous sheet and this

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Population Status and Trend of the Maasai Giraffe in the Mid Kenya-Tanzania Borderland

Among the nine sub-species of giraffes, the Maasai giraffe is the most widespread and common in Northern and Southern Kenya. Although it’s considered by the IUCN to be a species of no conservation concern, they have been reported to have declined in some of their range areas mostly due to bush meat activities, habitat fragmentation and loss. There are also concerns recent climatic changes especially prevalence of droughts is increasingly becoming another threat to their survival. In this regard, this

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Does the risk of encountering lions influence African herbivore behaviour at waterholes?

A central question in the study of predator–prey relationships is to what extent prey behaviour is determined by avoidance of predators. Here, we test whether the long-term risk of encountering lions and the presence of lions in the vicinity influence the behaviour of large African herbivores at waterholes through avoidance of high-risk areas, increases in group size, changes in temporal niche or changes in the time spent in waterhole areas. In Hwange National Park, Zimbabwe, we monitored waterholes to study

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Scene From Above: Retinal Ganglion Cell Topography and Spatial Resolving Power in the Giraffe (Giraffa camelopardalis)

The giraffe (Giraffa camelopardalis) is a browser that uses its extensible tongue to selectively collect leaves during foraging. As the tallest extant terrestrial mammal, its elevated head height provides panoramic surveillance of the environment. These aspects of the giraffe’s ecology and phenotype suggest that vision is of prime importance. Using Nissl-stained retinal wholemounts and stereological methods, we quantitatively assessed the retinal specializations in the ganglion cell layer of the giraffe. The mean total number of retinal ganglion cells was 1,393,779

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Effects of simulated shoot and leaf herbivory on vegetative growth and plant defense in Acacia drepanolobium

Plants have considerable ability to respond to herbivory, both with (above-ground) regrowth and with increased defense. We simulated both leaf and shoot herbivory in controlled, replicated experiments on individuals of Acacia drepanolobium in Laikipia, Kenya. These experiments were carried out on individuals that had experienced different, experimentally controlled histories of large mammalian herbivory. Both forms of simulated herbivory were associated with compensatory regrowth. Branches whose shoots had been removed grew significantly more over the next year than paired control branches,

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Vegetation factors influencing density and distribution of wild large herbivores in a southern African savannah

Understanding factors influencing large herbivore densities and distribution in terrestrial ecosystems is a fundamental goal of ecology. This study examined environmental factors influencing the density and distribution of wild large herbivores in Gonarezhou National Park, Zimbabwe. Vegetation and surface water were predicted to have a stronger influence than anthropogenic-related disturbances (livestock grazing, fires, settlements and poaching) on the density and distribution of wild large herbivores. Aerial survey data for seven common wild large herbivores conducted in 2007 and 2009 and

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