COMMUNICATION
An example: greeting display in hyenas
Hyenas: powerful social carnivores in Africa
When hyenas meet, they greet each other with a strange display
Fundamental questions:
A) What do they do?
Naïve observer: two male hyenas attempt to impress each other by embarrassing the other male with the size of their penis
BUT these are FEMALE hyenas – not penis but pseudopenis. Baby hyenas are born through the bended birth canal &
elongated pseudopenis. Consequently, birth complications are common - first babies & young mothers often die
B) What is the origin of this signal? (HOW?)
Development of sexual organs in mammals…
S J Gould: male penis and female clitoris develop from the same
embryonic tissue
Tissue exposed to male sex hormones (testosterone and
androgens) during embryonic development penis develops
When tissue is NOT exposed to androgens clitoris develops
Study: Immigrant male – higher testosterone levels. Pregnant females
have similar testosterone levels to adult males.
C) What is the adaptive value of the signal? (WHY?)
Social rank is important in hyena clans…
Hyenas live in social groups (clans) led by females
, females are dominant over all males
High ranking mothers
- have cubs with higher survival rates than low-ranking mothers
- have high-ranking daughters
Potential explanations:
1. The pseudo-penis is a by-product of high ranks of mothers (and thus elevated androgen production of mothers)
non-adaptive explanation
The non-adaptive explanation is unlikely because
• testosterone concentrations in female spotted hyenas are similar to other female mammals, including Homo
sapiens
• testosterone concentrations in female hyenas are an order of magnitude lower than those of reproductively
active males
• formation of the penile clitoris and scrotum appear to be largely androgen independent, since experimentally
reducing the androgen levels of pregnant females did NOT produce reduced pseudo-penis in their daughters
2. Females may mimic males – having a pseudopenis is a useful trait in hyena society adaptive value
3. Pseudopenis gives females control over who to mate with adaptive value
Forms and context of communication
Communication: the process in which actor(s) use specially designed signals (or displays) to modify the
behaviour of reactor(s)
Signal: any trait (or behaviour) that is designed to alter the behaviour of one
(or more) receivers
An example: greeting display in hyenas
Hyenas: powerful social carnivores in Africa
When hyenas meet, they greet each other with a strange display
Fundamental questions:
A) What do they do?
Naïve observer: two male hyenas attempt to impress each other by embarrassing the other male with the size of their penis
BUT these are FEMALE hyenas – not penis but pseudopenis. Baby hyenas are born through the bended birth canal &
elongated pseudopenis. Consequently, birth complications are common - first babies & young mothers often die
B) What is the origin of this signal? (HOW?)
Development of sexual organs in mammals…
S J Gould: male penis and female clitoris develop from the same
embryonic tissue
Tissue exposed to male sex hormones (testosterone and
androgens) during embryonic development penis develops
When tissue is NOT exposed to androgens clitoris develops
Study: Immigrant male – higher testosterone levels. Pregnant females
have similar testosterone levels to adult males.
C) What is the adaptive value of the signal? (WHY?)
Social rank is important in hyena clans…
Hyenas live in social groups (clans) led by females
, females are dominant over all males
High ranking mothers
- have cubs with higher survival rates than low-ranking mothers
- have high-ranking daughters
Potential explanations:
1. The pseudo-penis is a by-product of high ranks of mothers (and thus elevated androgen production of mothers)
non-adaptive explanation
The non-adaptive explanation is unlikely because
• testosterone concentrations in female spotted hyenas are similar to other female mammals, including Homo
sapiens
• testosterone concentrations in female hyenas are an order of magnitude lower than those of reproductively
active males
• formation of the penile clitoris and scrotum appear to be largely androgen independent, since experimentally
reducing the androgen levels of pregnant females did NOT produce reduced pseudo-penis in their daughters
2. Females may mimic males – having a pseudopenis is a useful trait in hyena society adaptive value
3. Pseudopenis gives females control over who to mate with adaptive value
Forms and context of communication
Communication: the process in which actor(s) use specially designed signals (or displays) to modify the
behaviour of reactor(s)
Signal: any trait (or behaviour) that is designed to alter the behaviour of one
(or more) receivers
