Different factions of the abolitionist community are arguing about this question (here and here), which surprises me. You'd think the answer was obvious: of course men can be feminists. In fact, you'd think advocates for animals would reach that conclusion especially quickly, and in unison.
Background: I like to use the word "animalist" as a term for animal advocates who challenge traditional views about the moral status of non-human animals--whether they're utilitarian, rights-oriented, abolitionist, feminist care-oriented, etc. I think of the word "animalist" on the model of "feminist". Like feminists are strong advocates for women, aiming to lift women out of their traditional inferior role, animalists aim to raise the status of non-human animals. The parallel makes it particularly perplexing that anyone would doubt that men can be feminists. Human animals aren't just capable of being animalists--i.e. advocating strongly for non-human animals; they're the only animalists. Non-human animals obviously can't advocate for themselves, in any articulate and effective way. Humans' being members of the "oppressor class" clearly doesn't stop them from adopting an animalist mission and perspective. Sure, there are some limits on our ability to imagine what it is like to be a captive chicken, but that doesn't stop us humans from trying, and from being adamantly pro-chicken.
Likewise, surely, the man who advocates for women. A man can't know exactly what it's like to be a woman, but he's in no worse position (surely) than someone who tries to understand and advocate for chickens. If there are no male feminists, then there are no human animalists. All animalists should therefore immediately agree: since there are (obviously) human animalists, there can also be male feminists. I only wish there were more of them!