How can giraffes detect and avoid predators

For some species, risk can be reduced further by herding with a diluting partner i. A diluting partner may reduce predation risk from a shared predator by having different detecting abilities. Such mixed-species effects on risk likely reflect a heightened ability of the mixed group to detect approaching predators compared with single species herds. This mixed-species effect has been shown to reduce personal vigilance in a number of species Scheel ; van der Meer et al.

This reduction in vigilance allowed the cattle to spend more time foraging Kluever et al. For example, body size can influence potential predation risk, with smaller species having greater predation risk and exhibiting higher vigilance levels than larger species Sinclair et al. Therefore, herding with smaller species should be more beneficial than herding with larger species, as long as the species share the same predators i.

Alternatively, large-bodied species may be less negatively influenced by visual constraints, such as vegetation, when detecting predators. Therefore, small herbivores could potentially enhance their fitness by herding with larger species whose detecting abilities are less diminished by habitat structure. The association of giraffe Giraffa camelopardalis with other herbivores has led to the assumption that giraffe may benefit other coherding species e.

However, there is no scientific evidence to support this assumption. Moreover, giraffe only rarely produce audible alarm snorts Schaller ; Moss Thus, eavesdropping on alarm calls cannot be the main mechanism by which coherding species reduce their predation risk. Nevertheless, giraffe do exhibit an easily identifiable staring posture when in the presence of predators Dagg This posture is most likely a cue, which is an incidental feature that does not have intended meaning to a receiver Saleh et al.

As a result, it may be possible that individuals can learn about potential threats by observing the reaction a cue of other members in their group e. For example, in gray kangaroos Macropus giganteus , a species that does not produce alarm calls, conspecifics cue off the reactions of other group members to predators to gain information regarding threats Pays et al.

However, whether one species can react to the posture of another i. Consequently, the aims of this study were to 1 determine whether the presence of giraffe can reduce zebra vigilance because they share the same key predator i.

We expected that due to the height advantage of giraffe, that zebra would reduce their time spent vigilant and rely more heavily on information gathered from coherding giraffe.

Additionally, we predicted that giraffe may have a greater impact on zebra vigilance behavior compared with wildebeest because not only are they a diluting partner, but due to their height advantage, zebra may perceive the quality of information from giraffe to be better. If this was the case, then we expected that zebra would focus more of their vigilance toward giraffe and rely less on personal scanning of the environment.

Alternatively, we may find that zebra are unable to decipher nonaudible cues i. We conducted fieldwork during August—September late dry season and December wet season To minimize habitat differences in perceived predation risk, we limited observations to herds feeding in savannas with visibly similar tree cover.

However, within a savanna, there can be differences in the tree:grass ratio that could influence perceived predation risk Stears and Shrader and ultimately vigilance Metcalfe Giraffe tend to avoid woody habitats, particularly with young, and select open savannas where personal vigilance and speed of escape are facilitated Young and Isbell Thus, we assumed in our study that giraffe selected similar habitats and small-scale differences in tree:grass ratios would not result in differences in vigilance levels.

To control for variation across our study sites, we included a site effect in our statistical analysis. Additionally, we collected data 2h after first light and 2h before last light to maintain the same level of perceived predation risk across days as per Scheel ; Schmitt et al.

All observations occurred from a stationary vehicle using binoculars. To avoid potential behavioral changes due to vehicles, we only collected data when no other vehicles were present and when the zebra were more than 20 m from the road. In a study of lion prey preferences, Hayward and Kerley found that across 48 different lion populations, giraffes were the 4th most preferred prey item, whereas zebra were the 7th most preferred prey item.

Because both zebra and giraffe are categorized as favored prey items for lions Hayward and Kerley , these herbivores gain the benefit of both dilution and detection when herding together i.

A study by Schmitt et al. In this study, we were only interested in the effects of detection in reducing vigilance levels. Therefore, to make vigilance comparisons between herds as a result of detection, we limited data collection to similar small-sized zebra-only and zebra—giraffe herds that we encountered i. We collected data from adult zebra of both sexes, but avoided herds that contained zebra or giraffe juveniles. Vigilance observations started when a focal zebra had its head down and was grazing.

We considered zebra being actively vigilant when they lifted their head above grazing height and scanned for predators, or focused their gaze and actively listened as per Scheel ; Schmitt et al. Due to the placement of their eyes on the side of their head, zebras can use monocular and binocular vision Barnett As a result, they can see to their side using monocular vision while they forage Harman et al.

This ability could potentially allow zebra to be passively vigilant while they feed and thus detect approaching predators. However, because zebra head placement while feeding is pointing toward the ground, we are unable to differentiate between zebra being passively vigilant looking for potential predators using monocular vision or searching for another foraging patch.

Furthermore, it is unlikely that the level of passive vigilance shown by zebra while foraging will differ between zebra-only and zebra—giraffe herds. Thus, we restricted our data collection to active forms of vigilance Scheel ; Creel and Winnie ; Creel et al. To explore whether the presence of giraffes influenced zebra vigilance, we compared active head raised zebra vigilance when herding in zebra-only herds, with zebra herding in zebra—giraffe herds.

We observed a zebra for 3min and recorded: 1 time spent actively vigilant, 2 intensity of each vigilance event i. A focused scan comprised a zebra staring in a fixed direction, with its ears pricked, either looking toward another herd mate i.

With regard to source of information, when herding in a zebra-only herd, a zebra could obtain information about predation risk by looking at a conspecific, conducting its own scan of the environment, or both.

For zebra, binocular vision oriented in the direction of the muzzle provides better depth perception compared with their side-orientated monocular vision Harman et al. As a result, it is more likely that these herbivores would use binocular vision to actively scan for approaching predators. Thus, we considered zebra being actively vigilant when their head was raised and their muzzle was directed toward a zebra, giraffe, or out to the environment.

If zebra looked at 2 sources separately in a scan e. However, if a zebra directed a scan toward a zebra and a giraffe, and we could not discern which individual was the focus of the scan, we recorded the scan as toward an unknown target.

Finally, to explore the relative influence that giraffe have on zebra vigilance behavior, we compared the amount of time zebra spent vigilant when herding with giraffe and when herding with a known diluting partner—wildebeest. We collected zebra vigilance behavior in the same manner as described above. These data come from Schmitt et al.

Prior to statistical analysis, we calculated mean individual vigilance per herd i. To test whether time devoted to vigilance was influenced by herding with giraffe, we tested for herd independence to ensure the data could be pooled. There was no herd effect; thus, individual herds were independent.

Therefore, we used the mean time a herd was vigilant as our dependent factor. We used an analysis of covariance ANCOVA to test whether the mean time spent vigilant by the herds varied with herd type zebra-only and zebra—giraffe.

The covariates such as number of giraffe, total number of ungulates, and season were nonsignificant and thus removed from the final model. Data were box—cox y transformed prior to analysis. To determine the relative impact of giraffe herding with zebra compared with when zebra herd with a known diluting partner, wildebeest, we used an ANCOVA with time spent vigilant as the dependent variable. We used herd type zebra—giraffe and zebra—wildebeest as the main effect and number of zebra in a herd as the covariate.

Initially, we also included site, season, and total number of ungulates as covariates. However, these were nonsignificant and thus removed from the final model. These data are from Schmitt et al.

To test whether the intensity of vigilance events varied between zebra in zebra-only or zebra—giraffe herds, we compared the proportion of general versus focused scans within each herd.

Therefore, each herd had a proportion for a general and a fixed scan. We were able to differentiate between these proportions by including the independent variable, scan type. By including both these proportions for each herd type, we were able to determine if there was any change in the proportional use of each behavior as herd type changed.

Covariates site iMfolozi, Kruger , total number of ungulate individuals in a herd, and season were nonsignificant and removed. 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 The animal's elevated vantage point allows them to notice humans approaching from a distance. It is therefore unlikely that they can be surprised by an approaching person. To reach water, it has to splay its front legs and bend its knees before bending its neck to get its head down to ground level. When they raise and lower their heads its brain is protected by a special system of elastic blood vessels in the neck.

This system is effective in getting blood and oxygen to their heads, as well as to prevent blackouts when they lower their heads. They have enormous hearts, which weigh close to 25 pounds, and large lungs to effectively circulate air through the 6 to 8 feet long windpipe.

Their jugular veins have a series of one-way valves that prevent them from getting a rush of blood to their brains when they bend down.

Because it is not easy for them to lie down or get up quickly, sleeping is a huge inconvenience in their lives. Adult giraffes sleep standing up but hardly ever sleep for longer than five minutes at a time.

A wandering bull tests the reproductive condition of females he encounters by sniffing her urine. A female that becomes receptive for mating will be approached by a series of increasingly high ranking bulls.

In the Serengeti, nearly all the calves are born in traditional calving grounds to which a female will return. While it is still wobbly on its legs its mother guides it with nudges of her head and forelegs. Sadly the main reason for this is human population growth which results in habitat loss and illegal hunting. Not many people realize that the United States provides a market for the trade-in giraffe parts. It is estimated that 21 bone carvings, 3 skin pieces ,and 3 hunting trophies were imported into the United States during the last 10 years.

Did you know that these graceful African animals are already extinct in seven African countries? African Wildlife Detective. Want to discover some fascinating Giraffe facts you may not know? Ever wonder why Giraffes have black tongues, or why they have horns?

External and internal parasites cause them various diseases which affect their quality of life, further reducing their short life expectancy. Among the external parasites, there are about 15 types of ticks and fly larvae. Anthrax and rinderpest are diseases that not commonly or frequently attack them, but when an epizootic affect a population, some get temporarily blind and die.

For the giraffes, their risk does not end escaping from the dangerous animals, because their worst predators by far are humans.

The natives consider them a source of meat when others are scarce. They also believe that the tails of giraffes are good luck so that they try to get one. The human being is also considered a dangerous predator to giraffes. The populations living in the north have reduced their numbers dramatically for two main reasons: degradation of their natural habitat and poaching, which is the case in Kenya, Somalia, and Ethiopia, despite the fact that national parks are struggling to preserve them.

In some villages, those tails are used to create jewelry, collectibles for tourists, and even flyswatters for the huge mosquitoes out there. The coats are spectacular due to their thickness and the design of the different spots that each giraffe has.

Also, many of these animals become nothing but the trophy of hunter that want to say they have killed an exotic animal. While most areas of Africa make it illegal to harm or to kill a giraffe due to their conservation status it occurs on a regular basis. Villagers are desperate to make money so they will do what they can to survive. Rafferty, John. P Grazers Britannica Guide to Predators and Prey. Britannica Educational Publishing. Journal of Animal Ecology.