Diurnal, Nocturnal, Cathemeral Activity Patters

Diurnal primates are active during the day. The benefits include better visual foraging and visual communication. However, diurnal primates face increased predation, possible heat stress, and competition for food from birds and other primates.

Nocturnal primates are primarly active at night. They are better protected from predators and have fewer competitors for food. However, they cannot forage as extensively and socializing is difficult. Nocturnal primates tend to utilize vocal communication during hours of darkness when sound travels better due to humid night air. Nocturnal primates also have enlarged eyes that allow more light to penetrate (see Tarsier to the right).

Many primates are actually active throughout a twenty-four hour period on a sporadic basis. This is a pattern known as CATHEMERAL activity. This type of activity pattern means these primates sleep periodically throughout the day.

Can you think of possible benefits that would come from a Cathemeral activity pattern?

Prosimians Pongids Gibbons New World Monkeys

Old World Monkeys Primate Anatomy Locomotion Reoriented Use of Senses

Larger Primate Brains Primate Environments Dentition Primate Diets

"Social organization" Primate Evolution Infant-Mother Bond and Childhood Diurnal and Nocturnal Behaviors

Dominance and Hierarchies Human Organization as Bands One Final Thought Introductory Page

Prosimians	Pongids	Gibbons	New World Monkeys
Old World Monkeys	Primate Anatomy	Locomotion	Reoriented Use of Senses
Larger Primate Brains	Primate Environments	Dentition	Primate Diets
"Social organization"	Primate Evolution	Infant-Mother Bond and Childhood	Diurnal and Nocturnal Behaviors
Dominance and Hierarchies	Human Organization as Bands	One Final Thought	Introductory Page