Adaptations to Desert Conditions Adaptations to Desert

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Adaptations to Desert Conditions
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Adaptations to Desert Environments

• We will consider adaptations made by plants and
  animals to desert conditions such as
• High light
• High temperatures
• Fluctuating temperatures (day/night)
• Dry air - with somewhat random rain events
• Dry soil
• Lack of cover for protection from predators

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Leaf adaptations

• Leaf reduction (size)
• Increases surface area, but reduces water loss

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Leaf adaptations (cont)

• Leaf reduction (loss)
• Permanantly lost (eg. cacti) or lose during the
  dry seasons

Ocotillo
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Leaf adaptations (cont)

• Succulent leaves
• Heavy cuticle and succulent tissues
• Leaf color
• Light coloration

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• Spines - protection from excess solar insolation
  and predators
• Orientation toward sun

Grizzly bear cactus
Bisnaga
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Roots

• 21 root ratio is common (11 common in
  non-desert areas)
• May penetrate 5 meters and spread for 20 meters.
• Cacti have rain roots
• Only form after the soil has become moist
• Root buds rapidly elongate in moist soil
• When the soil dries these roots die
• Main woody root dehydrates

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Amphibians

• Water reserve in the bladder or as subcutaneous
  water
• Desert toads can accumulate from 30-50 of total
  body weight in bladder water
• Ability to absorb water through the skin
• Can burrow
• No definite breeding season
• Nocturnal activity

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Burrowed, created a hard earthen shelter,
secreted a membrane
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Lizards

• Body heat comes from 3 main sources
• radiation from sun
• conduction from substrate
• convection from the air

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• Regulate temperature by behavior
• Often sits in opening of burrow until body
  temperature is 38-40o
• Buried lizards may expose their head for a time
  before starting other movement.
• Move in and out of shade
• May climb into bushes when temp. is high
• Some change color with temperature changes
• Some pant at high temperatures
• Lay flat against rock when needing to raise
  temp. stand high when they need to cool

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Ectotherm activity
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Lizards

• Many use burrows of other animals
• Water storage - adaptations for some species
• fatty tissue in tails to hold water
• accessory lymph spaces along lateral abdominal
  folds to the head region.
• more water in the blood

Fringed toed lizard
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Lizards - sight

• Some nocturnal lizards - vertical pupils with
  several tiny notches paired opposite each other
• When closed, the pupil leaves a series of
  pinholes.
• Each forms an image by itself.
• Images are superimposed

Gecko
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Mammals

• Many burrow.
• A nocturnal habit for some.
• Some predators have also adopted a nocturnal habit

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Mammals

• Many burrow.
• A nocturnal habit for some.
• Some predators have also adopted a nocturnal
  habit
• Ectopic storage of fat

Fat-tailed sheep
Zebu cattle
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Jack rabbit (hare) Fox

• Large ears are effective heat loss organs
• Will use shallow burrows made by other
  organisms.
• Large ears fairly common means of losing excess
  heat in a number of mammals

Bat eared fox
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Eland and Oryx

• Cooling through the circulatory system

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Antelope Ground Squirrel

• Color varies
• Burrows in winter
• Tail used for shade
• Orientation

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Heat regulation - insects
Temperatures shown are at ambient temperatures of
15º and 35º C
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Birds

• Often nest building and reproduction are tied to
  rainfall
• Cooling is done through evaporative water loss
  to a large extent.
• May be through gular flutter -
• Particularly in goatsuckers
• Occurs with panting in quail, mourning doves and
  rock doves.

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Crimson chat (Australia)
Goes great distances to where rain has fallen to
build its nest and rear its young.
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