You're amphibolizing...you're using a vague, ambiguous expression to generate a fallacious argument.
The phrase "obligatory social species" can be understood with two different meanings -- meanings that don't imply each other.
1. It can mean, "a species that has no option but to be social." It's "obliged to be social," in the sense that it lives in groups.
2. It could be understood to mean, "a species that has moral obligations."
But arguing that a species is, in sense 1 "obligatory" does not at all suggest, as in sense 2, that it has "moral obligations." That second one would have to be shown: for there are species which are, in sense 1, "social" but behave in ways we would not at all characterize as "moral" or as even "morally capable." Male lions in prides kill cubs to put the females into early estrus. Killer whales are known to kill sharks and then just rip out their livers and leave the rest floating. Hippos kill anything that they find even slightly irritating or inconvenient. Many primates cannibalize their own kind...
Being a social animal does not imply morality at all. To be honest, you'd have to drop the word "obligatory," or disambiguate it, and then prove your case. For sense 1 does not go even one step toward indicating sense 2.