Garbage dumps do not harm wildlife. Evidence is furnished by the Masai

Can someone give a concrete explanation on why A is rejected?

Garbage dumps do not harm wildlife. Evidence is furnished by the Masai-Mara reserve in Kenya, where baboons that use the garbage dumps on the reserve as a food source mature faster and have more offspring than do baboons on the reserve that do not scavenge on garbage.

Each of the following statements, if true, casts doubt on the argument EXCEPT:

A) The baboons that feed on the garbage dump are of a different species from those that do not. - WRONG. It might so that the garbage feeding species populate more that that do not, thereby raising doubt over the argument.

B) The life expectancy of baboons that eat garbage is significantly lower than that of baboons that do not eat garbage. WRONG. Again doubts.

C) The cholesterol level of garbage-eating baboons is dangerously higher than that of baboons that do not eat garbage. - WRONG. Similar to above A and B.

D) The population of hyenas that live near unregulated garbage landfills north of the reserve has doubled in the last two years.

E) The rate of birth defects for the baboon population on the reserve has doubled since the first landfills were opened. - WRONG.

The blue text is key to understanding the passage.
Passage says garbage dumps do not harm wildlife. Question stem asks that the choices cast doubt on this argument i.e. it harms. But we need to choose the one that does not cast doubt i.e. dumps do not harm, eventually strengthening the passage.

Answer D.

Garbage dumps do not harm wildlife. Evidence is furnished by the Masai-Mara reserve in Kenya, where baboons that use the garbage dumps on the reserve as a food source mature faster and have more offspring than do baboons on the reserve that do not scavenge on garbage.

A) The baboons that feed on the garbage dump are of a different species from those that do not.

So the author is making a comparison within a particular species of baboons...the ones that feed on the garbage and the ones that do not.
However Option A says that the species of baboons are not same but different..which renders the comparison invalid, thus weakening the argument.
We need an option that either strengthens the argument or stays neutral...Hence A is wrong.