the energetic reward of going big the advantage of consuming large meals in the namaqua dwarf adder n.
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The Energetic Reward of Going Big The Advantage of Consuming Large Meals in the Namaqua Dwarf Adder. Bryan Maritz a,b & Graham Alexander a a School of Animal, Plant & Environmental Sciences University of the Witwatersrand b Department of Ecology and Evolutionary Biology

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the energetic reward of going big the advantage of consuming large meals in the namaqua dwarf adder

The Energetic Reward of Going BigThe Advantage of Consuming Large Meals in the Namaqua Dwarf Adder

Bryan Maritza,b & Graham Alexandera

aSchool of Animal, Plant & Environmental Sciences

University of the Witwatersrand

bDepartment of Ecology and Evolutionary Biology

Cornell University

huge meals come with costs and benefits
Huge meals come with costs and benefits

Benefits

Costs

Increased energy intake

Increased handling costs

  • High costs of digestion
  • Lost time
  • Increased predation risk
  • Increased risk of food poisoning
  • Physical hazards of eating huge meals
huge meals come with costs and benefits1
Huge meals come with costs and benefits

Benefits

Costs

Increased energy intake

Increased handling costs

  • High costs of digestion
  • Lost time
  • Increased predation risk
  • Increased risk of food poisoning
  • Physical hazards of eating huge meals

But, we don’t know the increase in energy intake because we don’t know how frequently large meals are encountered by wild snakes

Q: What energetic advantage can a predator derive from the capacity to eat super-sized meals?

slide10

Bitis schneideri

  • Small-bodied (mean SVL = 200 mm)
  • Structurally simple habitat
  • Easily quantifiable prey community
  • Feeds year-round
slide11

Merolesknoxii

TL = 162 mm

Mass = 4.3 g

Bitis schneideri

TL = 115 mm

Mass = 4.3 g

what are dwarf adders eating
What are Dwarf Adders eating?
  • Field records (n = 13)
but what is on the menu
But what is on the menu?
  • 6 arrays of 9 pit-fall traps (10L plastic buckets)
  • Trapped for 10-15 days at a time
  • Trapping covered all seasons
  • Totaling 4185 pitfall trap-days
  • Captured 240 prey animals from 10 species
  • 0.057 captures.bucket-1.day-1
  • No seasonal variation in community structure (ANOSIM: R = -0.005; P = 0.52)

10 m

10 m

6 x

what does this mean from energy intake
What does this mean from energy intake?
  • Individual-based model to estimate encounter rates and energy intake for typically-sized Bitis schneideri
    • Assumed that prey was eaten in proportion to encounter rate
    • Conversion from wet-mass of prey to an energy values based on measures from the literature
    • Adjusted these to account for assimilation efficiency, also from published data
    • Ran the model for 1000 iterations
what does it all mean
What does it all mean?
  • With the tight link between energy reserves and reproduction in snakes, these super-sized meals may determine whether a snake reproduces in a given year.
  • Our measures indicate that without the energy from large meals, Namaqua Dwarf Adders could not maintain populations at the study site… or probably for their range in general.
slide20

Thank you

  • Ernst Oppenheimer & Son
  • Namaqualand Mines
  • South African National Biodiversity Institute Threatened Species Programme
  • Rufford Small Grants Foundation
  • University of the Witwatersrand Research Council
  • University of the Witwatersrand Animal Ethics Screening Committee (2007/68/1 and 2007/69/3)
  • Northern Cape Province Department of Tourism, Environment, and Conservation (Permit 0914/07 and FAUNA 698/2009)
  • Wessels Family