California Deserts

1. California Deserts

2. Deserts • Defined as a region that receives less than 10” of ppt a year • Irregular • Temperature extremes • Windy • Nutrient poor alkali soils • Low rates of primary productivity • High rates of evapotranspiration

3. Low Irregular Precipitation

4. High Light Intensity • 90% reaches ground • High solar radiation • High UV

5. Temperature Extremes • Dry desert air holds little moisture • Water moderates temperature • 50 F temp change between night & day

6. WINDY!!

7. Nutrient Poor Soils • Low rates of decomposition • Aeolian soils • Low primary productivity • Alkali & salinity

8. High rates of evapotranspiration • Potential evapotranspiration is higher than precipitation

9. California Desert Animals • Amphibians- 16 • Reptiles- 56 • Birds- 425 • Mammals- 97

10. Desert Challenges for Animals • Water loss • Temperature

11. Water Loss • Cutaneous water loss • Insensible perspiration • Excretory water loss in urine and feces • Respiratory water loss • During breathing

12. Temperature • High summer daytime temperatures • Direct & reflected solar radiation • Conduction • Radiation • Convection

13. Desert Strategies • Expire • When the going gets tough…. die • Evade • When the going gets tough….leave • Endure • When the going gets tough…take it

14. Expire • Die or go into dormancy during harshest times of year

15. Alkali Fairy Shrimp • Live in desert playa • Only wet after rains • Water must persist for 1 week • Spend most life as dormant egg • 1/125 of an inch • 50-600 per sq ft • Salinity prevents eggs from hatching

16. Evade strategies • Seasonally migrate to an area where conditions are more hospitable

17. Deer • Mule • Larger • Stiff legged gait • Antlers branch in equal forks • Black tipped tail • White tailed • Bobbing gait • Antlers branch from main beam • Migrate up in elevation in summer • 100+ miles

18. Torpor/Estivation • Reduces water loss • Saves energy • Decrease temperature difference between body and outside • Rate of energy expenditure goes down • Saves water • Lower metabolism decreases water loss • Less evap by less breathing • Less urine & feces

19. Crepuscular Activity • Active at dawn and dusk when temperatures are moderate

20. Nocturnal • Active at night • Allows escape from hot daytime temperatures • Bats, snakes, rodents, foxes

21. Banded Gecko • Nocturnal • Escape heat and predators • Active body temperature 18F cooler than daytime active lizards • Distribution limited to regions with above 75F night temperatures

22. Ways to endure… • Adaptations t be able to function during

23. Endure lack of water • Store water • Tail fat • Bladder • Conserve water • Microhabitat choice • Minimize water loss in skin • Reduce loss from breathing • Reduce water loss in urine or feces • Tolerate dehydration • Lose lots water out of their bodies without dying ex desert toads

24. Banded Gecko • Store water to endure dry summer months • Tail fat storage • Can survive up to 9 months • Caudal waving to attract predators

25. Desert Tortoise • In spring eat moist foods • Green annuals and fruits • Plantago, legumes • Consume 3-4% of weight/day • Stores water in bladder • Up to 1 cup • Water stored in bladder used to process waste during drier times • Uses uric acid instead of urea to minimize water loss

26. Water Conservation • Strategies for reducing water loss

27. Microhabitat Choice • Stay in cool or moist microclimate • Moisture in environment reduces water lost through evaporation and respiration

28. Desert Tortoise • Hottest & driest months of year spent in burrow

29. Tarantula • Burrows in unsuitable times of year • Uses fangs and pedipalps to construct a burrow • Up to 20in deep • Provides escape from heat of day • At night moves to entrance to hunt • Plugs opening during winter • Dormant up to 28 months

30. Scales • Reduces cutaneous water loss • Skin with keratinized scales • Keratin water repellant • Reduce water loss

31. Western Coral Snake • Related to cobra • 2x toxic as rattlesnake • Neurotoxic • Small short fangs • Nocturnal • Active after rains

32. Scorpion • Cuticle on carapace reduces water loss • Nocturnal • Subterranean • Underground most year active 3-6 mo • Tolerates high body temp • 113F for over 1 hr • Low metabolic rate • Reduces respiration rate • Spiracles close • Guanine • Eliminates more nitrogen and requires less water

33. Don’t Sweat It! • Not using evaporative cooling conserves water

34. Reducing Excretory water loss • Protein waste product is urea • Requires significant water to eliminate • Elimination of waste in the form of uric acid reduces water required to eliminate waste • 10x less water than urea to eliminate the same amount of waste • Semisolid paste

35. Concentrated Urine & Dry Feces • Add more waste product (solutes) to urine so eliminating more for a given loss of water • Reabsorb more water during feces production

36. Nasal Water Condensation • Evaporative cooling in the nasal passageways cools exhaled air • Cooler air holds less water than warm air • Water in cooled air in nasal passageways condenses • Causes “rain” in nasal cavity • Retains water • Longer narrower nasal passages found in many desert rodents cools air further and condenses more water

37. Water from food • Acquire water metabolically from the breakdown of food • Carbohydrates & lipids release water • 1g carbs yields .5g of water • 1g lipids yields 1g of water • Protein consumes water

38. Kangaroo Rat • Long hind legs • Saltatorial locomotion (hopping) • Saves energy when moving in an environment with widely dispersed food resources • Allows turning and bobbing to escape predators • Large head with large hearing apparatus • Large eyes • External cheek pouches

39. Kangaroo Rat • Nocturnal • Days spent in cooler humid burrows • Block burrow entrance to keep temp & predators out • Metabolic water from carbohydrates & fat in seeds • Can survive entire life w/out drinking water • Concentrated urine • Kidneys concentrate urine 4-5x more than humans • Dry Feces • 50% less water content than human feces • 5x as dry as lab rat feces • Nasal water condensation

40. Desert Toads • Amphibians breath through moist skin • Results in 15x more water loss/hr than rattlesnake • Spend most of year underground buried in soil or in deep rock crevices • Couch’s Spadefoot up to 2 years buried

41. Desert Toads • Water storage in bladder • Up to 30% body weight • While dormant store waste (urea) in tissues to save water • Tolerate levels that would be toxic in other species • Excess solutes in tissues assists toads in absorbing water from surrounding soil

42. Endure Temperature • High temperature challenging for body function • High temperatures increase water loss

43. Reduce Heat Input • Minimize solar

44. Common Chuckwalla • Large herbivorous • Leaves, flowers, fruits • Large size accommodates diet • Extract 60% of energy from food (vs 90% of insectivorous lizards) • Large intestine in large torso can fit greater volume food needed to get equal energy

45. Common Chuckwalla • Summer moisture and food are at critical low • Remain in rock crevices for days at a time • Reduces temperature & energy requirements up to 70% • Survive on stored fat and water • Water acquired metabolically only, do not drink

46. Common Chuckwalla • Dry vegetation of late spring has little water and high levels of salts • Reduce water use by eliminating salt by discharging out of nostrils

47. Microhabitat choice • Stay out of sun

49. Long-tailed Brush • Hides in creosote bush • Early morning orients in direct sun • Late morning increases time in shade • Afternoon moves to base of bush to exposed roots • May bury in sand

50. Woodrat • Creates midden • Elaborate nest built of tunnels and piles of debris • Debris acts as thermal blanket • Up to 4ft tall • Provides protection from predators and temperature