What Constrains Daily Intake in Thomson’s Gazelles?

Wilmshurst, John; Fryxell, John M.; Colucci, P. E.

doi:10.1890/0012-9658(1999)080[2338:wcdiit]2.0.co;2

Cited by 64 publications

(100 citation statements)

References 51 publications

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“…According to the forage maturation hypothesis (FMH; Fryxell, 1991), the daily intake of digestible nutrients is highest on swards of intermediate height because of the inverse relationship between the abundance and the quality of plant tissues. This has been confirmed in ruminants by estimating daily rates of energy gain in relation to grass biomass (Wilmshurst et al, 1999a and1999b;Drescher et al, 2006), and many studies demonstrated that animals select for patches with intermediate biomass (Wilmshurst et al, 1995(Wilmshurst et al, , 1999a(Wilmshurst et al, and 1999b. In our study, the effect of grass height on feeding site selection by horses was strongest in the H pasture where there was more variation in height; the animals selected the shortest heights which is a typical pattern for horses in temperate grasslands (see references in Mé nard et al, 2002).…”

Section: Discussionsupporting

confidence: 79%

Influence of sward structure on daily intake and foraging behaviour by horses

Fleurance

Duncan

Fritz

et al. 2010

Animal

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The spatial heterogeneity of grasslands determines the abundance and quality of food resources for grazing animals. As plants mature, they increase in mass, which allows greater instantaneous intake rates, but the cell wall concentrations increase too, reducing diet quality. In ruminants, daily intake rates are often constrained by the time needed for the ingesta to pass through the rumen, which is influenced by the rate of digestion. It has been suggested that the digestive constraint should have much less effect on hindgut fermenters such as equids. Horses play an increasing role in the management of grasslands in Europe, but the data on the influence of the heterogeneity of the vegetation on their daily intake and foraging behaviour are sparse. We report here the results of a preliminary study concerning the effects of sward structure on nutrient assimilation and the use of patches of different heights by horses grazing successively a short immature, a tall mature and a heterogeneous pastures (with short and tall swards). Daily nutrient assimilation was higher in the heterogeneous pasture compared to the short (135%) and the tall (155%) ones. The digestive constraints may have limited voluntary intake by horses on the tall swards. In the heterogeneous pasture, the mean height used for feeding (6 to 7 cm) by horses was intermediate between the heights used in the short (4 to 5 cm) and tall pastures (22 to 23 cm), and the animals may thus have benefited from both short swards of high quality and tall swards offering a higher instantaneous intake rate.Keywords: foraging, functional response, horses, nutrient acquisition, sward heterogeneity ImplicationsThe horses maximised their digestible organic matter intake (DOMI) on the pasture, where a wide range of sward heights was available. They appeared to benefit from using both short swards of high quality and tall swards offering a high instantaneous intake rate. These results suggest that nutrient assimilation by horses is affected both by digestive constraints (the time needed to process food from tall mature swards) and by the availability of good quality (short) swards. If these results are confirmed, it will be necessary to re-evaluate the concept of 'horse-sick' pastures.

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Section: Discussionsupporting

confidence: 79%

Influence of sward structure on daily intake and foraging behaviour by horses

Fleurance

Duncan

Fritz

et al. 2010

Animal

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“…Shipley et al (1999) successfully predicted browse selection from considerations of diet quality, and it has been noted that browsers respond to both food quality and availability by eating a higher-quality diet and taking less from each plant at high food densities (Vivås & Saether 1987;Andersen & Saether 1992;Shipley & Spalinger 1995). This suggests that diet optimization under digestive constraints may be the fundamental process in browser foraging, as it appears to be in other mammalian herbivores (Belovsky 1978;Fryxell 1991;Doucet & Fryxell 1993;Wilmshurst, Fryxell & Colucci 1999). As Fortin, Fryxell & Pilote (2002) make clear, the important question is one of time-scale.…”

Section:       mentioning

confidence: 95%

Mechanisms of functional response and resource exploitation in browsing roe deer

Illius¹,

Duncan²,

Richard³

et al. 2002

Journal of Animal Ecology

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Summary1. The functional responses of roe deer were examined using 11 plant species. A technique to discriminate between encounter-and handling-limited processes was used, and it can be concluded that the functional response applicable to patch browsing by roe deer is governed not by the rate of encounter but by the rate of oral processing. 2. The large differences between plant species were due to variations in both parameters of the functional response: h , the time lost in biting, and R max , the maximum processing rate. Removing the thorns from three of the species affected these parameters differently, according to the size and density of thorns. 3. Animals took larger bites from larger patches (branches), and bite mass declined as patch exploitation progressed, implying that animals were selecting the larger items to eat first. It was demonstrated experimentally that depletion of the larger bites does occur first, and it was concluded that prey selection is an important component of herbivore foraging behaviour. 4. The gain curves for deer feeding on the different plant species are calculated as being virtually linear. Patch depression did not, in general, occur because increasing bite rate compensated for declining bite mass. Our mechanistic approach is contrasted with other approaches to describing the gain curve in the literature. 5. A priori and empirical grounds are presented for rejecting the hypothesis that resource exploitation by browsing mammals is governed by optimal patch use. Diet optimization, involving a trade-off between diet quality and quantity, offers a better explanation of herbivore foraging behaviour.

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“…The present results for the smallest grazer, Thomson's gazelle, conform to previous study in the area (Wilsey 1996). Thomson's gazelles are known to make more utilization of areas with sward of low to intermediate biomass (Wilmshurst et al 1999;Fryxell et al 2004). In the Serengeti, burnt areas carry low phytomass and have a relatively short sward compared to vegetation in non-burnt patches ), a situation which favours Thomson's gazelle requirement.…”

Section: Patch Contrastsmentioning

confidence: 99%

Fire history and management as determinant of patch selection by foraging herbivores in western Serengeti, Tanzania

Hassan

Rija

2011

International Journal of Biodiversity Science, Ecosystem Servic

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Although the use of fire as a management tool has increased during the past decades in East African savannas, there is insufficient knowledge about herbivores' utilization of areas with different fire history. We therefore examined large mammal herbivores' preference for patches that differed in fire history to test whether herbivores would non-randomly select patches according to availability. Our study area was the East African Serengeti ecosystem. Animals were recorded along transects at monthly intervals from May 2001 to April 2006, and data on the burnt and non-burnt areas along transects were extracted from existing fire maps. The prediction was tested using chi-square goodness-of-fit test, and selection ratio as a preference index for patch types. Our results show that African buffalo persistently occurred in non-burnt patches, whereas browsers (Giraffe and Kirk's dik-dik) and mixed feeders (Grant's gazelle and impala) were often seen in non-burnt patches but also used burnt patches. Grazer species (Thompson's gazelle, topi, wildebeest and Burchell's zebra) favoured patches burnt in the current year compared to non-burnt patches. For all species together, patches burnt repeatedly were least selected compared to those that were burnt only once in 3 years. The outcome of this study suggests that annual burning of the same patches is not optimal for biodiversity maintenance and ecosystem functioning.

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What Constrains Daily Intake in Thomson’s Gazelles?

Cited by 64 publications

References 51 publications

Influence of sward structure on daily intake and foraging behaviour by horses

Influence of sward structure on daily intake and foraging behaviour by horses

Mechanisms of functional response and resource exploitation in browsing roe deer

Fire history and management as determinant of patch selection by foraging herbivores in western Serengeti, Tanzania

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