Introduction to Commensalism

• Josh, Chuck, and Jerry discuss commensalism on "Short Stuff" podcast
• Topic discovered while researching symbiosis on howstuffworks.com
• Commensalism: one animal benefits from another organism by doing its own thing
  • Benefiting organism unaffected one way or other
  • No tit-for-tat exchange, no harm
  • One-way cooperation

Defining Commensalism vs Other Relationships

• Not parasitism: parasite causes harm to host (like movies Parasite, Alien)
• Not mutualism: both partners benefit (like bees and flowers, movie Wall Street reference)
• Not symbiosis: more aligned with mutualism
• Commensal = organism that benefits
• Commensal requires other animal to go about daily business for survival

Eastern Screech Owls and Blind Snakes Example

• Eastern screech owls eat blind snakes (favorite delicacy)
• Owls bring blind snakes to nest to feed chicks
• Some blind snakes escape, burrow deeper into nest
• Escaped snakes feed on larvae/bugs in nest
• Larvae would be parasites on owl chicks
• Benefits: owl hatchlings with blind snakes in nest grow bigger, faster, stronger
  • Lower mortality rate vs nests without blind snakes
  • Blind snakes reduce parasite load
• Blind snake just eating normally, unaware of benefit provided

Personal Anecdotes

• Chuck's owl cafe experience in Tokyo
  • Could hold owls, pet them
  • Acknowledged captive conditions but well-cared for
• Josh's upcoming Disney World trip
  • Staying at Animal Kingdom
  • 3 park days: Magic Kingdom, Hollywood Studios, Universal
  • Daughter will love Toy Story Land at Hollywood Studios
  • Shoutout to Brandon (Disney employee/friend helping with tips)

Three Categories of Commensalism

• Ecologists admit difficulty defining commensalism but maintain 3 categories

1. Inquilinism

• Species lives on/inside another
• Examples:
  • Blind snake in owl nest
  • Gopher tortoise tunnels (Southeastern US)
    • Tunnels 30-50 feet long
    • Home for insects and other animals
    • Some evolved to need living there
    • Moth species: feeds exclusively on keratin from dead gopher tortoise shells
    • Various animals likely lower parasite loads for tortoises

2. Metabiosis

• Organism unintentionally creates habitat for another
• Josh's skepticism: examples can be ascribed to symbiosis/parasitism instead

3. Phoresy (P-H-O-R-E-S-Y)

• Animal physically attaches to another for transportation
• Example: mite catches ride on bee
  • Mite travels from "mightville to my town"
  • Bee unaffected (as long as mite not feeding on it)
  • If mite feeds on bee = parasitism, not commensalism

Josh's Critique of Commensalism Classification

• Believes many "commensalism" examples are actually symbiosis
• Gopher tortoise hole animals eating parasites = symbiosis (mutual benefit)
• True commensalism very rare in nature
• Suspects ecologists created sub-discipline from flawed initial understanding

Ecosystem Impact of Commensalism

• Can put entire ecosystem under stress
• Example: moth dependent on gopher tortoise keratin
  • If gopher tortoises die off, moth species also dies
  • Initial bonanza followed by starvation
• More commensalism = shakier ecosystem foundation
• Ideal: biodiverse species that can stand alone
• Avoid full interdependence where species can't exist without others