12 - strepsirrhines Flashcards
misconceptions about strepsirrhines
Often portrayed inappropriately as ‘basal’,
‘primitive’ or inferior primates
- anthropocentrism
- smaller and less complex brains than haplorrhines
Hinders understanding of strepsirrhine, primate,
and mammalian evolution
- e.g., in the lemurs, natural selection has driven an
isolated population of primates to diversify to fill
a rich variety of ecological niches
strepsirrhines in numbers
1/3 of all living primates
lemuriformes the largest group of strepsirrhines
now -110 species of living lemur, in 5 families and 15 genera
103 threatened species, 33 critically endangered
evolutionary history
Lemurs rafted from Africa
to Madagascar
Lorises split from African
galagos around 40 mya
and later colonised Asia
adaptive radiation
A single species rapidly diversifies into many new species
Evolution of new morphological and physiological traits that allow
organisms to exploit different environments
bamboo and bamboo lemurs
Abundant food source, little competition. Contains cyanogenic glycosides, which release hydrogen cyanide when chewed (bitter, and toxic)
Greater bamboo lemur (CR) eats mature stalks
Up to 90% of diet of golden bamboo lemur
(CR) is tender shoots (even more cyanide!
Craniodental adaptations to process the bamboo mechanically
As yet unknown digestive/ metabolism system
adaptations to process large daily doses of cyanide
aye-aye
Largest nocturnal primate
Percussive foraging
Only extant member of the genus Daubentonia and family Daubentoniidae
Endangered
Giant aye-aye extinct <1000 ya
lucky lemurs
- no other tree dwelling mammals on Madagascar
- few predators
-few competitors - 2? successful colonisation events
- fill niches
- different to mainland africa
extant lemur ecology
- Madagascar
- Wide range of habitats
- Except central plateau (mostly treeless)
- Rivers divide island into
smaller biogeographic
regions - natural barriers for range
expansions of many species?
lemur ranges vary
some species e.g. grey mouse lemur cover almost the length of island
others have some of the smallest known ranges among living primates
lorisformes
africa and asia -10% living primates
taxonomy, evolutionary history, and biogeography poorly understood
two families:
galagidae
lorisdae
galagidae
- galagos or bushbabies
- 6 genera
- sub-Saharan Africa
- west African rainforest to South African
acacia woodlands - True diversity unknown
- New taxa continue to be discovered
- Precise range of individual taxa and their
conservation status unclear
lorisdae
5 genera, 16 species
Angwantibos and pottos in Africa
slender, slow and pygmy slow lorises in Asia
strepsirrhine body size
smallest living primate (mouse lemur 30g) to some of the largest known primates (>150kg)
largest extant strepsirrhines <10kg
galagids and lorisids 50-1500g
all lemurs sexually monomorphic or females slightly heavier. lorisforms males 5-20% heavier than females
tree living
- all lemurs primarily arboreal
- locomotor specialisation like vertical clinging and leaping in Indriidae
- only ring-tailed lemur and some Eulemur spend lots of time on the ground
- all lorisforms exclusively arboreal
-some galagos show pronounced leaping
what do strepsirrhines eat (1)
Dietary diversity greater than in haplorrhines
Extreme specialists and many generalists:
Some lorises almost exclusively
faunivorous
Fork-marked lemurs specialise on tree
gum and sap (>85% of feeding time)
Some sportive lemurs and avahis spend up to 100% of their feeding time on leaves,
buds, and flowers
what do strepsirrhines eat? (2)
Gentle lemurs (Hapalemur and Prolemur) are bamboo specialists
Ruffed lemurs (Varecia) almost exclusively
frugivorous
All other species combine these majorcomponents regularly or seasonally
Distribution and availability of different types of food have important implications
for ranging patterns, competitive regimes, and life history adaptations
energy saving primates
lemurs spend day in tree holes,
some lemurs (several species of cheirogaleus and microcebus as well as allocebus) hibernate for up to 7 months during the barren dry season
life history
what kills strepsirrhines
Predators of lemurs
- Raptors (owls, hawks, and eagles), snakes, carnivores
(mongoose, fossa), introduced carnivores (dogs and cats)
- Much larger predators went extinct along with larger subfossil
lemurs
Predation rates on lemurs among highest in primates
- Relatively small
- Relative lack of other mammalian prey on Madagascar
Predators of lorisiforms
- snakes, viverrids, and other primates (orangutans, chimpanzees)
Pathogens
Intrinsic mortality
- Starvation, disease
- Mating season for males in some species
activity and vision
All lorises and galagos nocturnal
Most extant lemurs nocturnal
Diurnal activity evolved independently 2-4 times in
lemurs
Hapalemur and Eulemur are cathemeral
- irregular bursts of activity around 24-h cycle
Trichromatic colour vision in some diurnal lemurs;
maybe some cathemeral lemurs
Galagos have monochromatic vision
Some variation in colour vision reported for lorises
evolution of social systems
Strepsirrhines show diversity of social systems
Almost all forms found in haplorrhines
Long independent evolution
Similarities and dissimilarities with
anthropoids -> general principles of primate social evolution
social organisation
size composition, cohesion and genetic structure of a social unit:
- solitary
- pair
- group
all 3 occur in strepsirrhines
solitary species
- up to 1/3 primate species
- ancestral for all strepsirrhines
- most lorisforms
- often association with nocturnal activity
- behavioural ecology not as studied
solitary not asocial
- mothers associate with their offspring
- some individuals sleep in groups
- widespread communication among neighbours by sounds and odours
- individuals meet conspecifics regularly
- highly complex lifestyle and challenging to study
the myth of the uniform solitary primate
Rich intra- and inter-specific variation in social organisation of solitary primates
Differences in sleeping group composition and
interactions
Theoretical and empirical work has focussed on
why most primates live in groups
Selective pressures favouring solitary life remain
unclear
Benefits of feeding on non-shareable resources
outweigh antipredator benefit of being
gregarious?
pair living
- smallest permanent cohesive social units
- rare in mammals
- twice as common in primates (about 10%) than in other mammals
- up to 1/3 lemur species
- evolved independetly in several families and independent of activity period or body size
pair living lemurs
- some pairs rarely interact or sleep together
- use vocal duetting to synchronise activities at a distance
- home ranges of pair partners coincide
- both sexes defend the same home range
- minimal overlap with ranges of other adults
group living
permanent cohesive groups with 3+ adults that coordinate their activities closely
- evolved at least twice in lemurs (in lumeridae and indriidae)
- no group-living lorises and galagos
- group-living lemurs among largest extant species
- all at least partially diurnal
group living lemurs vs group living haplorrhines
- lemur groups smaller, controlling for body size and phylogeny
- relatively even adult sex ratios
- some types of social organisation found in haplorrhines have not evolved in lemurs
mating system
Pattern of observed mating interactions
Reproductive system—who reproduces with whom—can only be determined with genetic paternity analyses
Male reproductive strategies determined by distribution of receptive females in space and time
various mating systems in strepsirrhines
mating systems
social structure
nature and patterning of interactions between pairs of individuals.
nature frequency and intensity of affiliative and agonistic interactions
-> relationships
social structures of nocturnal strepsirrhines poorly understood
dominance
competition for resources favours dominance relationships when conscpecifics interact regularly, one individual consistency shows submissive behaviour towards the other which reduces probability of costly fighting.
leads to dominance hierarchy at group level
dominance examples/not examples
ring tailed lemurs form largest groups, with linear hierarchies, stable over several years among females
red fronted lemurs - most dyads do not maintain dominance relations; no clear hierarchy at group level
sifakas - dominance relations exist but low interaction rates make them difficult to define
male-female relationships
Widespread female dominance over males
All adult females consistently elicit submissive behaviour from all adult males in dyadic interactions in all
behavioural contexts
Facilitated by lack of sexual size dimorphism
Not found in other primates
Rare in other mammals
Remains unexplained!
