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Colombia has a population of about 100 "cocaine hippos" founded from a group of one male and three females, which escaped from a drug kingpin's private zoo; it's even estimated that this population could grow to over 1,000 in the next two decades or so:

The rise of the so-called "cocaine hippos" began in 1993 after authorities killed Pablo Escobar and seized his luxury estate Hacienda Napoles, about 250km (155 miles) north-west of the capital Bogotá.

Animals found there were distributed to zoos across the country, but not the hippos. "It was logistically difficult to move them around, so the authorities just left them there, probably thinking the animals would die," Ms Castelblanco said.

Instead, they thrived.

Over the years, scientists have tried to calculate how many hippos are living in Colombia's waterways, with estimates ranging from 80 to 120 animals. "It is the biggest hippo herd outside Africa, which is their native region," veterinarian and conservationist Carlos Valderrama told the BBC. [...]

Ms Castelblanco and her peers say the population will reach over 1,400 specimens as early as 2034 without a cull - all of them descended from the original group of a male and three females.

I'm curious however if these "cocaine hippos" don't show any signs of inbreeding depression given how small the founding group was. Are there any studies/articles on this aspect in that Colombian hippo population?

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    $\begingroup$ I found one publication of Hippo population genetics from 2015 in Mol. Ecol. but they sadly didn't feature the Columbian population, actually it seems there is very little research going on regarding this Cartel-neozoa -bloat. Sadly some people are trying to get them on birth control animalbalance.org/hippos . They could be of great value for the fields of population genetics, evolution, invasive species ecology, as well as ecosystem engineers ecology. $\endgroup$ – user12256545 Feb 13 at 13:32
  • $\begingroup$ Well, is there a report that they don't suffer from inbreeding depression? $\endgroup$ – pascal Feb 13 at 13:42
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    $\begingroup$ @user12256545 *Colombian. Columbian is the exchange. $\endgroup$ – Rodrigo de Azevedo Feb 13 at 14:00
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    $\begingroup$ biology.stackexchange.com/q/98252/27148 seems like approximately the same question asked a different way. $\endgroup$ – Bryan Krause Feb 13 at 14:20
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    $\begingroup$ It then seems you gave yourself an answer. $\endgroup$ – pascal Feb 13 at 14:53
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Answer: Its highly likely they are suffering from inbreeding depression,or will be at least soon, since the founder population size (n=4) is three magnitudes low of the literature value for the minimal viable population size. Even if there is no genetic evidence in form of a published study, this is a super clear case with such a restricted gene pool.

An MVP of 500 to 1,000 has often been given as an average for terrestrial vertebrates when inbreeding or genetic variability is ignored. When inbreeding effects are included, estimates of MVP for many species are in the thousands. Based on a meta-analysis of reported values in the literature for many species, Traill et al. reported concerning vertebrates "a cross-species frequency distribution of MVP with a median of 4169 individuals (95% CI = 3577–5129)."

source:

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