The other situation is if mom has O type blood. The same thing can happen as with the (-) and (+) blood type difference, but it is not as severe. If mom has O+ or O- blood type, and the baby has A+, A-, B+, B-, AB-, or AB- blood type, an ABO incompatibility can develop.
Why do howler monkeys howl? Howler monkeys live in family groups in the rain forests of South America. They howl so that other monkey groups do not stray into their territories. The sound also helps group members stay in contact with each other. Monkeys are communal animals that live in exclusive groups.
Howler monkeys are among the largest primates in the Neotropics. They can grow to be 22 to 36 inches tall when standing. And, their tails are about the same size in length as their bodies! Male howlers are black, while females are brown. They have prehensile tails that they can use to grab onto branches.