Are there any animals who are struggling with something relate to evoutionaly concepts?

You could look at various populations that have been subjected to habitat fragmentation.  Just putting a road across an ecosystem may divide the ecosystem in half, and top predators such as wolves will have smaller populations and hunting territories.  Extensive fragmentation may result in small areas unable to support a viable breeding population.

Humans are the main cause of loss of habitat among other animals. For example there was a group of dolphins called the Yangtze river dolphins (because they lived in the Yangtze river) also known as Baijis, but river pollution from factories and boats changed the pH of the water and also meant it contained toxic substances rendering it extinct.

Another interesting one, was many loggers driving through the Amazon rainforest reported that they kept 'accidentally' hitting birds with their trucks because the road cut through the path which the birds took. It has also been speculated that these birds were eating the tobacco from discarded cigarettes and got addicted to nicotine, this meant they went back to the road regularly to find more tobacco to feed the nicotine addiction and this meant lots of birds were waiting in the road.

There are many more such as the giant panda of which there are less than 2,000 in the wild because the natural habitat in the bamboo jungles have been cut down for human use.

Another one could be the polar bear struggling to survive as the ice caps are melting and they cant rest on land and die of exhaustion from swimming in the sea too long, something which they are not adapted to do.