If hippopotamuses cannot swim, how did they colonize islands?

Abstract

. 2014: If Hippopotamuses cannot swim, how did they colonize islands?. Lethaia, Vol. 47, Owing to their aquatic lifestyle, hippopotamuses are normally believed to have reached islands by swimming. Yet, some studies suggest they cannot swim due to their relatively high density. If so, this raises the question of how hippopotamuses would have reached some islands. Their immigration into the British Isles, Sicily, Malta, Zanzibar and Mafia can be accounted for, because these islands sit on continental shelves and were often linked to the mainland during the Pleistocene glacio-eustatic sea-level falls. In contrast, their occurrence in Crete, Cyprus and Madagascar would be more difficult to explain. Available geological evidence does not seem to rule out that the latter islands might have been connected with the nearest mainland areas in very recent times. This study intends to consider possibilities about how hippopotamuses reached islands and to show that more effective collaboration is required among specialists involved with the study of insular evolution, colonization and speciation. □ Dispersal events, extra-Mediterranean islands, glacio-eustatic sea-level excursions, Mediterranean islands, Pleistocene.

If hippopotamuses cannot swim, how did they colonize islands: a reply to Mazza

“…Mazza () lists Cyprus, Madagascar and Crete as cases for which there is, or should be, geological evidence for a Pleistocene land bridge connection. First of all, Mazza exaggerates the various distances to the mainland of these islands.…”

“…Sweepstakes routes, such as tsunami‐like transportation, swimming or natural rafting are supposed to result in an insufficient number of founders to establish themselves (Mazza ; p. 3). We do not agree with this unsubstantiated statement.…”

“…How hippopotamuses managed to cross tens or even hundreds of kilometres of open sea to islands and why they did so are, as Mazza () formulates it, challenging problems. The formidable body mass, barrel‐shaped build and the relatively stocky, short limbs do not look as those of an apt swimmer.…”

“…Yet, the fossil record proves their existence on six islands during the Pleistocene. Mazza (, p. 2) suggests they were on ‘probably most other Mediterranean islands’, but there is no evidence to support this claim, despite the abundant fossil record from Sardinia, Corsica, the Balearics, Tilos, Rhodes and Karpathos. Arguing that hippopotamuses cannot swim in open sea, Mazza postulates that in all of these cases the only remaining option for colonization is by land bridge, either fully exposed or only one or two metres deep.…”

“…If Mazza is right, and hippopotamuses cannot survive overseas dispersal, the available geological evidence should be reconsidered or an alternative explanation has to be looked for. There are some inconsistencies in Mazza's reasoning, which we address below in light of effective collaboration among biologists, palaeontologists, geologist and biogeographers as recommended by Mazza ().…”