Inbreeding in Big Cats: Consequences and Conservation

[Pckts]

(08-23-2023, 11:31 PM)Balam Wrote:

(08-23-2023, 09:28 PM)Pckts Wrote: Inbreeding/line breeding is a natural occurrence. Neither good nor bad. While bad traits and immune responses are doubled the good traits are as well. Especially with line breeding which is why you saw such a strong population in Tadoba from Wagdoh lineage and Machli in Ranthambore. 
You always want new blood which may offer stronger and different immune responses but they also may bring in bad blood that dilutes an otherwise strong population.

Have the tigers from this area been the subject of genetic studies to assess the level of inbreeding and genetic health? You do bring an interesting point in regards to line breeding which typically involves mating animals that are related, but not as closely related as in traditional inbreeding. The thing is that this is an entirely controlled practice that we can't happen in the wild with the same rigour it does in captivity.
 
The case that sparked this conversation with the jaguars being reintroduced into the Iberá wetlands represents direct inbreeding which can cause a serious genetic bottleneck down the line, even if the animals inbreeding may appear superficially very healthy.

This is why in areas where populations of animals are isolated and not connected through natural corridors the risk of extinction increases, because inbreeding make their immune system weaker, drops their fertility, and increases mortality. Constant inbreeding also causes a reduction in size from successive generations and may be one of the reasons why Amur tigers and Asiatic/West African lions do not achieve the same consistency in large sizes the may have in the past (in addition to precarious prey base). It's also specially worrying in the case of the lions because in theory a virus or disease can be lethal to the population in Gir given their possibly weaker immune systems. We are seeing this in the way the sperm of Asiatic lion has deteriorated due to inbreeding, which makes us wonder to what degree this has also occurred in Amur or Sumatran tigers.

"Fitzpatrick and colleague Jonathan Evans compared existing data on sperm fitness for 20 endangered and non-endangered species of mammals, including the Florida panther, Asiatic lion and cheetah. Scientists have previously observed extreme reductions in sperm quality for each of these big cats – all of which also suffered huge reductions in population size that led to inbreeding.


The team found that, on average, 48% of the sperm of endangered species was abnormal, compared with 30% in non-endangered species. In addition, the percentage of the sperm that was motile – or capable of movement – was around 10% lower in endangered species. Earlier research has shown that both characteristics make a male less likely to produce viable offspring."

More here.

If Predators are isolated they are more susceptible to extinction due to many factors. Their prey suffers the same as they do, the slightest imbalance can cause catastrophic outcomes. But when all things are equal, linebreeding and inbreeding occur often, I mention Waghdoh because Tadoba is filled with his progeny, the same with Ranthambore and Machli and any other place with a long standing dominate male/female. 
But like I said, it must be a balance, you always want new blood to introduce possible traits that could be beneficial but that new blood can be detrimental as well. 
There would be no dog breed today without inbreeding and linebreeding, humans followed this same pattern and it never affected their population increase. 
 
Point being, when you see a big, strong male cat you want his genes spread. You want him line bred throughout the territory and that's what happens, it's the natural cycle. Occasionally a new male comes in, runs him out and introduces his genes in hopes to accomplish the same. Whether this new male brings a positive result or negative one is completely random. Reply