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Living with Herds
Smith, Ars Technica , "This 2,year-old bark shield took a beating in an Iron Age fight," 31 May Police responded and herded them back into their pasture without incident. But the Panic Was Still Real. Send us feedback. Explore the year a word first appeared From the Editors at Merriam-Webster. A Drudge of Lexicographers Presents Dictionary Entries near herd Hercules stone Hercynian hercynite herd herd's-grass herdbook herdboy Phrases Related to herd the herd Statistics for herd Last Updated 28 Oct Look-up Popularity Time Traveler for herd The first known use of herd was before the 12th century See more words from the same century Keep scrolling for more More Definitions for herd herd.
Entry 1 of 2 : a group of animals that live or are kept together : a large group of people : common people : people as a group herd. Entry 1 of 2 : a number of animals of one kind kept or living together a herd of cows herd. Please tell us where you read or heard it including the quote, if possible.
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Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! Getting our ducks in a row on it. Data were transformed using arcsine square root. Finally, to determine the source s that zebras used to gather information about perceived predation risk, we used an Anova with proportion of scans regardless of the scan intensity directed toward an information source i.
We then used the interaction of herd type zebra-only and zebra—giraffe and information source as the main effects. Covariates site, season, and total number of ungulates were nonsignificant and thus removed.
Data were arcsine square root transformed prior to analysis. The covariate number of giraffe was nonsignificant, indicating that the presence rather than number of giraffe reduced zebra vigilance. This reduction indicates that zebra perceive information gleaned from giraffe to be more valuable than that from wildebeest. When herding alone, zebra used focused scans proportionally more 0.
However, when herding with giraffe, zebra used general scans proportionally more 0. This pattern was consistent across sites. Zebras herding alone actively scanned the environment 0. In contrast, zebra herding with giraffe actively scanned herd mates 0. Neither herd types extensively scanned both herd mates and the environment. Moving in groups is a key way in which animals reduce predation risk Krause and Ruxton However, for this to be possible, group members must be able to obtain information about potential threats from other group members Metcalfe ; Elgar A number of studies have shown that information about predators can be conveyed through alarm calls Seyfarth et al.
Our results show that when one or more giraffe were present in a group of foraging zebra, the time zebra devoted to vigilance dropped by nearly two-thirds compared with when herding with conspecifics.
Living with Herds: a vocalisation dictionary | Sentence first
Furthermore, in mixed-species herds, the majority of zebra scans were directed toward giraffe. Therefore, we hypothesize that the mechanisms through which this reduction occurs is likely because zebra are able to interpret the leaked cues e. As a result, zebra are able to reduce their perceived predation risk even in the absence of alarm calls. Interestingly, the amount of time that zebra devoted to vigilance when herding with giraffe was half as much as when they herded with wildebeest, a known diluting partner Schmitt et al.
Thus, it seems that zebra perceive these leaked cues from giraffe to be more valuable, and more reliable, than information from a similar-sized diluting partner. Furthermore, in zebra—giraffe herds, zebra relied more on general vigilance scans compared with the focused scans i.
Moreover, there was a near complete switch in behavior from relying on direct personal assessment of risk in zebra-only herds, to primarily using social information i. The switch in information source used by zebra is surprising because in mixed-species herds, zebra theoretically should use both conspecific and heterospecific cues equally to better determine predation risk Goodale and Kotagama , rather than relying mainly on cues from giraffe. However, this shift can potentially be explained by 2 reasons.
This is similar to other species that rely on elevated conspecific sentinels for antipredator information, such as meerkats Suricata suricatta Santema and Clutton-Brock Second, the large body size and the characteristic body language displayed by giraffe when they detect the presence of lion i. The information gained by zebra from giraffe is perhaps more accurate than information from conspecifics or other coherding species, such as wildebeest, because the height of the giraffe makes it less likely to be obstructed by vegetation.
For example, a study on 2 species of shorebirds Arenaria interpres and Calidris maritime found that with decreasing visibility there was an increase in individual vigilance Metcalfe This was because the shorebirds could not rely as much on antipredator information gathered from other members in the flock because they were obstructed from view, in addition to a greater risk of predation from hidden predators with decreasing visibility Metcalfe Thus, the information from giraffe is likely more valuable to zebra than information from conspecifics or similar-sized heterospecifics sharing the same predation risk.
This is likely because zebra can gain more information about predators e. If our interpretation is correct, this then raises the question, if zebra gain so much by moving with giraffe, then why do not they always herd with them? A potential reason for this is that giraffe may experience lower levels of predation by lions compared with zebra. In general, bigger-bodied animals are less sensitive to predation Sinclair et al. For example, Sinclair et al.
TO LIVE WITH HERDS
However, a meta-analysis of the prey preference of lions that covered 48 different lion populations found that giraffe were determined to be the 4th most preferred prey item, whereas zebra were only the 7th most preferred prey item Hayward and Kerley Thus, due to the risk of predation from lions, giraffe should maintain high vigilance levels.
Although this level may be less than that of zebras, our results suggest that the quality of the information i. Otherwise, why would they rely so heavily on the giraffe? However, if this is the case, then it does not explain why zebra and giraffe do not always move in mixed herds. A more likely reason for the lack of herding of zebra with giraffe may have to do with information that is gained beyond predator presence.
In our study, it was common for zebra to herd with giraffe, but they more frequently herded with wildebeest, impala, or a combination of these 2 herbivores. Specifically, because zebra are grazers, they do not gain foraging information by moving with browsing giraffe. Thus, the combination of these two factors may be more beneficial than the reduced predation risk provided by giraffe, hence explaining the more frequent herding by zebra with grazers and mixed feeders. However, when zebra herded with giraffe they did follow them and continue to feed in close proximity when the giraffe moved off Schmitt MH, Stears K, personal observation.
During our study, we did see giraffe herding with other browsing herbivore species including kudu and impala Schmitt MH, Stears K, personal observation.
https://axivetyzos.tk However, kudu and impala browse at a much lower height than giraffe Du Toit Therefore, similar to zebra, these browsing herbivores only gain a reduction in predation risk and no benefit from social information about the availability and location of food. This could explain why other browsing species do not continuously herd with giraffe. Ultimately, our data suggest that when in zebra-only herds, zebra primarily assess predation risk by directly scrutinizing their outward environment i.
However, when moving in zebra—giraffe herds, they shift and primarily rely on giraffe as a way of detecting predators. Thus, it would seem that for zebra in zebra—giraffe herds that the reliability of the information about predation risk is far greater than the benefits that zebra obtain by scanning the environment themselves. Additionally, the survival and fitness benefits obtained by eavesdropping on giraffe are greater than when herding with conspecifics or similar-sized diluting partners. We thank R. Schmitt and S. Holbrook who provided statistical advice and valuable comments on earlier drafts as well as S.