Xenarthra anteaters, sloths,

1
Xenarthra anteaters, sloths,
armadillosPholidotapangolins

• Xenarthra is from the Greek, meaning
  strange-jointed ones. With minor exceptions
  Xenarthrans are and have always been South
  American animals.
• Pholidota means scaled-skin animals. Pangolins
  are scaly ant- and termite-eaters of Africa and
  Southeast Asia.

2
Zoogeographical taxonomic riddles currently
being solved

• Xenarthrans are ancient, Southern-Continent
  animals. How come they are not found in Africa
  or Australia?
• Xenarthrans probably arose in Cretaceous, but
  first fossils date from c. 60MYBP Africa had
  separated by 80-65MYBP.
• South America-Antarctica-Australia dont break
  until c. 35MYBP, but climate stops land-dispersal
  c. 64MYBP.
• Thank you, geologists and paleontologists!
• At one time xenarthrans pangolins were put in
  one Order (Edentata). What really is their
  relationship?
• Formerly ambiguous, the resemblance is now known
  to be the result of extreme convergence.
• Pangolins closest relatives are probably
  carnivores.
• Thank you, molecular taxonomists!

3
Almost all mammalogists now accept three major
clades of eutherian mammals, but

• The fossil record gives us no decent clues as to
  which split is most profound.
• Statistical analysis of molecular evidence gives
  approximately equal support to each of the three
  hypotheses at right.
• What do you think that geo-history might suggest?

4
The Living Xenarthra
55MYBP
65MYBP
5
Some Xenarthran Geological History

• The Xenarthrans (MYBP)
• 80-65 Order originates
• 65-63 Armadillos split
• 55 Sloths AAs split
• 55-3.5 Moderately rapid speciation
  background extinction
• 3.5-2 Increased rates of speciation
  extinction.
• 11KYBP Extinction of almost all N.Am. Xenarthra
• 10KYBP Extinction of 90 of S. Am. Xenarthra
• 4KYBP Extinction of 100 of Caribbean Xenarthra.

• The Geo-Ecology (MYBP)
• 65 End of Cretaceous
• 55-3 World increasingly seasonal (dry in places)
• 3MYBP-10KYBP Ice ages Inter-glacials
• 2.5MYBP Panama rises great faunal interchange
• 10KYBP Rapid warming, increased rain sea-level
  rise, people in Americas mammals w/massgt 50kg
• North America lose 75
• South America lose 80
• 5-4KYBP People into Caribbean.

6
(No Transcript)
7
Probable patterns of xenarthran evolution

• Earliest types
• Ancestral form was probably a sloth-like,
  leaf-eating, cellulose fermenter.
• Offshoots eventually included
• Armadillos (the hard-skinned xenarthrans many
  fossils) were the first to split off. These were
  and remain successful ground-scroungers.
• Sloths and anteaters split later. These 2 groups
  eat very different stuff, but both groups
  food-types are difficult. Exact ancestry of
  anteaters is not definitively known.
• More on patterns of extinctions
• Circa 2MYBP Armadillos and specialists are more
  likely to survive overall losses less than
  formerly believed.
• Circa 10KYBP Big stuff is more likely to become
  extinct.
• Perhaps ecologists should not succumb to
  physics-envy.

8
Characteristics of living xenarthrans

• Backbone is highly flexible, but in 1 dimension
  only.
• Teeth (if present) lack enamel and are simple
  single-rooted.
• Smell is emphasized over other senses.
• All exploit difficult food resources
  (armadillos less so than sloths and anteaters).
• All survivors (except armadillos) are extreme
  specialists.
• All try to save thermoregulatory energy
• By low body temps and/or heterothermy.
• By behavior.
• By choice of habitat and/or microhabitat.

9
Some Representative Living Xenarthrans
10
Sloths in general

• Taxonomic diversity
• once much greater 60 fossil genera are known
• 2-toed 3-toed varieties are convergent 2-toed
  now classed w/ground sloths (Megalonychidae)
• But ecological similarity among living sloths.
• The problems of a leaf-diet
• Tropical ecology detoxifying leaves
• Digesting cellulose energetics ?

11
Adaptations (?) that are probably related to
sloth energetics

• Fermentation in compartmented stomach
• Cost of microbial symbiants
• Month-long throughput
• Feces and urine
• About 1-2 times per week (500ml urine!)
• Climb down from the tree why?
• Slow movement
• Labile body temperature
• 28oC-35oC (system-failure possible at 18o
  ambient)
• Range-restriction to tropical rainforest
• Adaptations to save energy
• Move slowly (hence the name)
• Insulate well have low body temperatures (must
  therefore live in tropics)

12
Three-toed sloth(Bradypodidae)

• Bradypus variegatus.
• 40-70cm 2.2-6.2kg.
• 8-9 cervical vertebrae flexible neck.
• Much slower than 2-toed sloth.
• Eats from one tree for very long time.
• Green fur (longitudinal slits and specific
  algae).
• 11 month gestation extensive maternal care.

13
2-toed sloth(count on front feet)

• Choloepus hoffmanni
• 6-8 cervical vertebrae
• More active, fiercer, and more catholic of diet
  than 3-toed variety.
• 50-55cm, 5-8.5kg.
• Highly variable body temps (24oC-35oC).
• Gestation 4-6months maternal care is protracted.
• Female-biased sex ratio (reportedly 11 to 1) in
  wild. (Why?)
• Animal is long-lived (often gt 20 years).

14
Sloth status and conservation

• They usually dominate Amazonian-mammal biomass
• 2-toed 2.7/ha
• 3-toed 7/ha
• The prefer Cecropia over other trees
• This genus thrives in second-growth forest.
• So habitat is not endangered.
• But they are reservoirs of Leismaniosiswhich you
  dont want!

15
Giant ground sloths (extinct)

• Ground sloths are placed in the Family
  Megalonychidae.
• Recall that two-toed sloths are placed in the
  same Family as ground sloths.
• Thus their resemblance to three-toed sloths is
  due to convergence.
• Ground sloths invaded North America before
  Panamanian land-bridge.
• At max diversity (c. 20KYBP)
• 15 genera of S. Am. ground sloths
• 4 genera of N. Am. ground sloths
• So extinction is probably not due to competition.
• What else might caused it?

Think 200kg-3000kg!
16
Anteaters (3 basic types)

• In the Neotropics, much of the zoomass is
  concentrated in colonial insects anteaters eat
  nothing else.
• Front legs are powerful each has a single,
  greatly enlarged claw (3rd digit). Guess why.
• Teeth are absent, but rostra are elongated
  ridged. Tongues are long sticky.
• Pyloric region of stomach is thickened and may
  serve as a gizzard for grinding chitinous
  exoskeletons (and as a protection against
  concentrated formic acid).

17
Type 1 small entirely arboreal

• Cyclopes didactylus
• 350g, lt50cm head-body.
• Entirely nocturnal.
• One author estimated 700-5000 ants/day (former is
  much too low).
• Only xenarthran for which paternal care reported
  (but is it true?).
• Male-overlap territorial pattern.

18
Type 2 Medium sized partly arboreal partly
terrestrial

• The genus Tamandua (gt 2 species) enters North
  America in southern Mexico.
• 2-7kg, 60cm head-body.
• Eats ants termites (about 9000/day).
• Tripod defense.
• 1 baby (rarely twins), extensive maternal care
  for up to about 1 year.
• Most common anteater.

19
Type 3 Large entirely terrestrial

• Myrmecophaga tridactyla.
• 20-40kg, 180cm total length.
• Female bears one young per year, nurses for 6mo.,
  carries on back for about one year.
• Often diurnal where not molested by people.
• Male-overlap territory.
• Most endangered by conversion of habitat for
  cattle ranching.

20
Ecologyof M. tridactylaHow do they manage???

• Adults need 14,000-28,000 insects/day
• Termites seldom eaten?
• Termites dominate diet?
• Taking so many from a single colony would destroy
  resource piecemeal.
• Giant anteaters typically hit c.100 colonies per
  day, eating c. 150-175 insects from each.
• Mourão radio-tracked 7 for 10mo. ranges did not
  asymptote.
• More?

21
Folks say that big mammals cant be
insect-specialists, but
50 fruit
22
Armadillos the most successful living xenarthrans

• Roughly 30 living species, mostly South American
  (one species ? USA).
• Armor (bone horn-like substance) is arranged in
  bands plates connected by flexible skin.
  (Shoulder hip shields, armored head legs,
  rings around body, underside soft.)
• Food is mostly invertebrates though small
  vertebrates considerable plant matter are also
  consumed.
• Respiration often anaerobic low metabolic rate.

23
Dasypus novemcinctussuccessful invader of USA
from the South

• Total length about 75cm mass c. 5kg (XX) 6.5kg
  (XY).
• Range is probably constrained bywell, who knows?
  (Dramatic range extensions in twentieth
  century.)
• In USA, gt 90 of diet is invertebrates.
• Reproduction is by monozygotic polyembryony (not
  characteristic of Order).

24
How did they get there? How far can they go?

• US range extensions
• Natural movements plus
• Introductions
• Hitch-hiking
• Limits ( non-limits) to range
• Physiological constraints perhaps not primary
• Vasoconstriction, shivering, increased
  metabolism
• (Look at Mo, Ok, Tx, Ks.)
• Food-supply may be more critical
• Global Warming the Armadillos that ate
  Manhattan?

25
Priodontes maximus

• 100cm h-b, 70kg (? still, largest living
  xenarthran).
• Once widespread across South American plains.
• Digs shelters, often in active termite mounds.
• Main food is termites ( a few ants feeding
  strategy not like giant anteater).
• Highly endangered by habitat modification and
  direct exploitation.

26
Cabassosus tatouay

• 20-45cm h-b, 5kg.
• Main food is fossorial insects (mostly ants
  termites?) sticky tongue.
• Middle claw greatly enlarged (root-cutting).
• Usually produces 1 baby/litter.
• Endangered by habitat destruction.

27
Tolypeutes matacus

• 30cm h-b, 1.5-1.8kg.
• Probably eats mostly ants termites.
• Karyotypically very different from all other
  armadillos (2n38 all other armadillos
  2n50-64).
• Bears single young.
• Only armadillo genus that can roll into a
  complete ball.

28
Chaetophractus Fairy armadillos

• This variable genus includes at least 3 species
  of small (c. 25cm) armadillos.
• Thermoregulatory strategy includes burrows
  several meters long.
• Chaetophractus includes much plant material in
  diet. It is known for burrowing under carcasses
  to obtain maggots.

29
Euphractus sexcinctus

• 40cm h-b, 3-7kg.
• South American dry seasonally inundated
  prairies.
• Spends most of day in burrow.
• Not commonly exploited for food.

30
Zaedyus the pichi

• Head-body length is 25-35cm.
• Food is typical of armadillos though pichis are
  said to include a fair amount of plant material
  in diet.
• These armadillos inhabit sandy soils in southern
  South America.
• Litter is 1-3 young weaning occurs at about 6
  months.

31
Family Glyptodontidae (extinct)

• Glyptodonts were distant relatives of armadillos.
• More completely armored.
• Larger grazers.
• Once, successful invaders of the North (including
  South Carolina).
• Possible causes of extinction
• Competition?
• Climate?
• People?

32
Order Pholidota (pangolins)

• Taxonomic position unclear once classified with
  xenarthrans in Edentata now believed to be more
  closely related to Carnivora.
• No teeth. Long, sticky tongues. Bodies covered
  with scales derived from agglutinated hairs.
• Pangolins can be highly selective in diet, often
  moving great distances (at night) and scraping in
  soil only lightly for preferred ant type.
• Pangolins pay role in traditional medicine and
  folklore ( are heavily exploited in some areas).

33
African pangolins

• Manis tetradactyla (top)
• M. temmincki (bottom)
• 60cm, 7-15kg.
• Burrow well and climb OK.
• Eat mostly termites (plus some ants).
• Mother carries single young on back or curled in
  tail.
• Can ball up completely.

34
Manis javanica an Asian pangolin

• Total length 80-90cm.
• Males are larger and are known to fight violently
  over females.
• Less armored than African species.
• An ant and termite predator estimated (uh, by
  whom?) to take about 70 million insects per year.