Megaherbivore
It is thought that the main cause of extinction was the flood basalt volcanic eruptions that created the Siberian Traps,[9] which released sulfur dioxide and carbon dioxide, resulting in euxinia,[10] elevating global temperatures,[11] and acidifying the oceans.
It is thought that ceratopsids fed on rugged vegetation, due to their jaw being designed for a crushing effect.
One mechanism is thought to have played a major role: an extraterrestrial impact event in the Yucatán Peninsula.
[19] For about 25 million years, the earth was void of large terrestrial herbivores that weighed more than 1 ton.
After this period, small mammalian species evolved into large herbivores across every continent around 40 mya.
These features allowed mammoths to live an expansive life because of the availability of grasses and trees.
[32][33][34] Scientists have proposed that increasingly extreme weather—hotter summers and colder winters—referred to as "continentality", or related changes in rainfall caused the extinctions.
[41][42] Giraffidae are a sister taxon to Antilocapridae, with an estimated split of more than 20 million years ago, according to a 2019 genome study.
[43] Rhinoceroses may originate from Hyrachyus, an animal whose remains date back to the late Eocene.
[38]: 17 Megaherbivores and other large herbivores are becoming less common throughout their natural distribution, which is having an impact on animal species within the ecosystem.
This is mainly attributed to the destruction of their natural environment, agriculture, overhunting, and human invasion of their habitats.
[44][45] As a consequence of their slow reproductive rate and the preference for targeting larger species, overexploitation poses the greatest threat to megaherbivores.
[44] Living species exhibit the following adaptations: they have dietary tolerance, a strong effect on vegetation and with the exception of calves, face little threat from predators.
[39] Due to their size, megaherbivores can defoliate the landscape; because of this, they are considered keystone species in their environment.
They can open up areas through feeding behavior, which over time clears vegetation, including invasive alien plants.
[4][51] In addition, megaherbivore grazers, like the white rhino, have a profound impact on short grass.
In one study, short grass became more infrequent after the elimination of white rhinos, which effected smaller grazers in the area.
[57] Giraffes may flee or act in a non-aggressive manner, while white rhinos typically do not react to the presence of predators.
[38]: 14 [58] Extant megaherbivores are K-selected species, meaning they have high life expectancies, slow population growth, large offspring, lengthy pregnancies, and low mortality rates.
They have selected slow reproduction to enhance their survival chances, and as a result, increase their lifespan.
[59][60] Their large size offers protection from predators, but at the same, it decreases the degree at which they reproduce due to restricted food sources.
[38]: 116–124 They usually give birth to a single calf that is heavily reliant on females for food and protection.
