Trouble at the Rockland (Mass.) Zoo: a mamba bites receptionist Joanne Nordstrom (who dies because someone's sabotaged the fridge that keeps the antitoxin cold); endangered-list red wolves savage manager Donald Stewart, who has taken too close an interest in the zoo's finances--now being handled by Alex Cristos (whose ``mouth formed a cool, saccharine smile that didn't impact the rest of his face'') and by Edward Hargreve, son of late director H.L. Hargreve--and there's growing evidence that H.L., apparently killed by Kenyan poachers, was professionally hit, maybe by the same guy who's leaving scheming Edward notes claiming that ``the lion's share is mine.'' Three more Homo sapiens will get put down before new vet Carlson MacIntyre can win a reprieve for those wolves by fingering the real killer--but since, as in most zoo mysteries, the animals are more varied and interesting than the humans on display, there's no cause for alarm. First-novelist Tate, teaming up with zookeeper Hanna (Monkeys on the Interstate, 1989), has succeeded in producing a genre piece that, like its intrepid protagonist, is ``tired down to [its] very bone marrow.''