ANT 154B Course notes- Lecture _3

ANT 154B Course notes- Lecture _3 - ANT 154BN Course notes...

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Unformatted text preview: ANT 154BN Course notes Lecture #3: Primate diets: core concepts 11 January 2011 Key terms and concepts are indicated in blue Outline 1. Overview of plant-primate interactions 2. Of guts and teeth 3. Fallback foods 4. The Jarman-Bell principle 1. Overview of plant-primate interactions Can be useful to consider issues from the perspective of the plant Leaves: plant food acquisition devices, which the plant wants to protect from primate herbivores, who use the leaves as a source of food --> arms race between plant chemical defenses and primate digestive anatomy and physiology Seeds: plant offspring, which the plant wants to protect from primate seed predators, who use the seeds as a source of food --> arms race between plant chemical and physical defenses and primate masticatory and digestive anatomy and physiology Fruit: vehicle for dispersal of plant offspring; sources of food for primates, plants want primates to disperse their seeds --> competition among plants to attract dispersers, competition between animal species who utilize the food resource --> leads to lots of specialization, in both fruits and their animal dispersers. co-evolutionary dynamics lead to syndromes 2. Of guts and teeth Primate diets differ, lots of differences between species and no species focuses solely on one type of food. Differences in diet have effects on morphology, shaped by natural selection Function: Teeth • penetrate foods’ physical defenses • fracture, grind, crush food • preparation for digestion • circumvent foods’ chemical defenses • extract nutrients, calories Guts ANT 154B Lecture #3 course notes Design features: Teeth (and other chewing apparatus) • number and relative size of different types of teeth • shape and height of crests • enamel thickness • jaw robustness and musculature Guts • stomach volume and extent of subdivision • microorganisms to digest cellulose • total surface area Teeth: Frugivores: • large, broad, incisors (piercing fruit husk) • rigid, bony palates (rubbing fruit against) • low, rounded molars (grinding) • strong lips (wadging) • seed specialists have very thick molar enamel Gumivores: • large prominent incisors (gouging holes in tree trunks) • some prosimians have “tooth comb” (scraping gum) page 2 of 5 Insectivores: Folivores: • sharp incisors, cusps (piercing exoskeleton, shearing prey) • high cusps, thin molar enamel; slicing, shearing crests • thin enamel creates very sharp edges Guts: Frugivores: • relatively simple guts • large stomach volumes (esp if large body size) • long small intestine (permits some hind-gut fermentation of fiber) Gumivores: • long caecum (extended period to digest and break down chemicals) Insectivores: Folivores: • short, simple gut (little specialization required) • need long, large gut (low quality foods) • specialized digestion & flora (to digest cellulose,etc) • enlarged large intestine with microorganisms OR large cecum with micro-organisms OR large, complex stomach ANT 154B Lecture #3 course notes Leaf eaters have relatively large stomachs Diet and gut morphology page 3 of 5 More leaves = bigger stomachs and longer guts Diet and gut morphology colobines Stomach surface area Percent leaves in diet Chivers 1994 Body weight 26 Leaf eaters have relatively large stomachs Tuesday, January 12, 2010 26 Chivers 1994 Relative stomach weight 27 More leaves = bigger stomachs and longer guts Tuesday, January 12, 2010 27 3. Fallback foods Reminder: diets vary substantially over time, because the availability of food varies A paradox: primates are dietary generalists, but are generally adapted to one class of foods. Why do they eat many types of foods, often ignoring foods they seem most well adapted to eat? Preferred foods are “selected”: disprop. Preferredused relative“selected”: foods are to their abundance. Fallback foods are eaten when preferred foods are scarce disproportionately quality food to their abundance Fallback foods are eaten when preferred foods +/- high used relative +/- low quality food a fe rr ed re r fe re d are unavailable. % of diet e Pr p nNo Consumption of fallback foods b availability of a food item Availability of preferred foods PreferredHigh quality foods foods are easy to process; Fallback foods are not Tuesday, January 12, 2010 Low quality foods 35 Therefore, species are adapted to processing their fallback foods, not their preferred foods. 34 Tuesday, January 12, 2010 (because preferred foods do not generally require specialized processing abilities) Selection acts intensely during times of resource scarcity; Individuals surviving “crunch” periods are those well adapted to processing fallback foods (e.g., Galapagos finches, redtail vs mangabey enamel thickness) Two kinds of fallback foods 1. “Filler FBFs”: Foods utilized only during periods of fruit scarcity but which never comprise 100% of the diet. 2. “Staple FBFs”: Foods utilized year-round, and which can seasonally comprise %100 of the diet. ANT 154B Lecture #3 course notes Hypotheses: page 4 of 5 1. FBFs can be classified as staples or fillers. Some species will have both types, but some species will not. 2. Species with staple food resources experience less pronounced fluctuations in resource availability. 3. Species with staples can form larger or more stable groups, possibly altering internal social dynamics. 4. The Jarman-Bell principle Jarman-Bell explains why primates with large bodies tend to live in large groups 1. a) Larger species consume less energy per unit body mass b) Larger species eat lower-quality food 2. Lower-quality food is more abundant 3. More abundant food allows bigger groups Jarman-Bell Principle Insect illustrated with insects and leaves Leaf Dietary quality Leaf Food abundance Insect 1 Group size Body mass Leaf 2 Dietary quality Group size Leaf Insect Insect 3 Tuesday, January 12, 2010 Food abundance Infanticide? 4 Body mass 54 “the folivore paradox”- eat what is assumed to be a ubiquitous resource, but small group sizes Why? infanticide? 86 C. M. Crockett and C. H. Janson I n f a n r i c i d e and g r o u p s i z e i .c C .J!l 0 E 0.75 I 0.5 0 0 .<: :;; a. 0.25 :2 :g .J!l " 0 0 .<: , 2 3 4 Average number of adult females F i g u r e 4.1. Deaths from infanticide per i n f a n t b o r n versus number o f females averaged over the entire 2-year study period (woodland data only). Numbers inside enlarged circles indicate number o f troops with identical x a n d y values. The regression line is plotted for illusrrarive purposes only. Red howler monkeys,oHatodMasaguaral,r Venezuela n t d e a t h rate ( ' , = 0 . 0 3 , NS, N = 2 4 , w o d l a n a n d gallery) o " o t b e r " i n f a w o o d l a n d ; ' , = 0 . 2 2 , NS, w o o d J a n d a n d gallery). T b e n u m b e r o f a d u l t females, a d u l t a n d s u b a d u l t males c o m b i n e dCrockettt & also was n o significantly correlated w i t h e i t h e r class o f i n f a n t m o r t a l i t y r a t e (woodland, N = 24: Infanticide, rs = 0 . 2 5 , NSj "other", rs = - 0 . 0 5 , NS; b o t h habi- Janson The weak effect o f male group size may result becau females associated w i t h l a r g e t male g r o u p s may be s a f e t from bouts following male incursions, they may be more vulner bouts r e s u l t i n g from s t a t u s changes a m o n g r e s i d e n t males. period March 1979 t o December 1981, ten successful a n d twO male i n c u r s i o n s were observed in t h e w o o d l a n d a n d galler associated with bouts o f infanticide. E i g h t o f t h e 1 2 incursion troops w i t h only o n e male a n d f o u r when ttOOps h a d two observed incursions occurred at significantly smaller male t h a n t h o s e e x p e c t e d a t r a n d o m from t h e d i s t r i b u t i o n o f m a l e d u r i n g t h e s t u d y period. S t u d y troops c o n t a i n e d 1, 2, o r 3 29.2%,46.6%, a n d 24.6% o f t h e s t u d y period, p r o d u c i n g exp o f 3 . 5 , 5 . 6 , and 2.95 incursions, respectively (chi-squared one xi = 9.17, P<O.05). Thus, larger male g r o u p size was associate risk o f incursion. However. the remaining three bouts o observed in the study occurred in tbe absence o f recent inc were instead related t o status changes a m o n g males. Such st w e t e identified in two t r o o p s w i t h twO a d u l t males a n d o n e s u a n d i n o n e w i t h t w o a d u l t males. I n f a n t i c i d e t i s k f r o m w i t h i n 2000uced in troops with more males. not red 56 Tuesday, January 12, 2010 Collsequences o fillfall ticidefor fectmdity offemales ANT 154B Lecture #3 course notes page 5 of 5 social stress? food is limited? Food for folivores is limited? Food for Red colobus monkeys, Kibale, Uganda folivores is limited? Snaith & Chapman 2005 Snaith & Chapman 2005 Tuesday, January 12, 2010 57 Red leaf monkeys, Gunung Palung, Indonesia Marshall, Boyko, Feilen, Boyko, & Leighton 2009 Tuesday, January 12, 2010 Marshall, Boyko, Feilen, Boyko, & Leighton 2009 58 Take home messages 1. Plants and primates have imposed strong and reciprocal selective forces on one another. 2. Design features of guts and teeth are shaped by natural selection to solve different challenges posed by different food resources. 3 Most adaptations for food processing are shaped by fallback foods, not preferred foods or most commonly eaten foods. 4. Large primates tend to eat low quality diets and live in large groups; small primates tend to eat high quality diets and live in small groups with exceptions that require additional explanation. Question to ponder* Do all foods in a primate species’ diet exert equally important selective pressures on their anatomy, physiology, and socio-ecology? Why? Be sure to briefly mention how food resources affect both anatomy and socio-ecology. ...
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