Cave Explorer Handout Verbatim Final
Cave Ecosystems
Case Study | Planet Earth | Episode 4: Caves
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'Closed' Ecosystems
The caves featured in this episode are unique in many ways. They contain entire and isolated ecosystems in which many odd species have adapted to suit the habitat niches available. Some caves contain species that are only found in that one place and the ecosystem must have been developing for millions of years in that one isolated place for these endemic species to develop.
Most ecosystems do not have boundaries that are easy to define. Animals and plants stray over any border that we draw on a map. They are Open Ecosystems. But in a few cases, it is difficult for organisms to enter or leave – an isolated pond or oasis, for instance, or a cave. In one, species are restricted by their need of water. In the other, by their ability to live in the dark. These odd examples are almost Closed Ecosystems – no system can be completely closed but these come close.
The Flow of Energy
In a normal ecosystem, the sun powers the growth of green material which is then eaten by herbivores and so on. Photosynthesis is the driving force. However, in the cave the sun does not penetrate and nothing grows, so where does the energy come from to start up the system?
The main source is the droppings of the bats and birds. They leave the cave to eat outside and excrete inside the cave, providing food energy for small invertebrate omnivores like cockroaches, the grazers of the cave. They are detritivores (detritus = waste). Larger invertebrates like centipedes then eat the cockroaches while micro-organisms break down the cockroach wastes. It is estimated that the bats eat up to 10,000kg of insects every night, bringing that energy into the cave. In more sealed caves, water flowing through may bring food sources like bacteria.
Adaptations & Extremophiles
The true troglobytes who never leave the dark are often strangely adapted. Animals like fish, salamanders and crabs will often lose the pigment in their skin and eyes as there is no value to being coloured and their eyes serve no purpose. Eventually, many have lost their eyes altogether and there are many example of blind cave creatures. This means that they must find their food by other means. Crabs can try and eat anything they find and some fish like the angel fish are filter feeders.
Extremophiles – organisms adapted to live in extreme environments. These include snottite bacteria which get food from toxic chemicals and exude sulphuric acid. Little cave fish live in highly acidic waters in huge numbers. In Antarctica, fish live in sea water so cold they should freeze but they have ‘anti-freeze’ in their blood.
Cave Dwellers
- Troglobyte: Never leave the cave. Specially adapted for the dark.
- Troglophile: Like caves but can also live outside.
- Trogloxene: Live in caves but leave to feed (bats).
Research Activities
Draw a food web based on this data:
- Bats/Swiftlets – eat outside, excrete inside
- Cockroaches – eat bat dung
- Centipedes/Scorpions – eat cockroaches
- Cave Cricket – eats bird eggs/nestlings
- Racer Snake – eats bats and swiftlets
Project Research
- • Gather examples of: halophiles, thermophiles, xerophytes, acidophiles.
- • Prepare a report, poster or presentation on their environments and lifestyles.
Field Notes
Ecosystem Role Activity
Role: Producer, Primary Consumer, Secondary Consumer, or Decomposer
Bats:
Cockroaches:
Centipedes:
Cave Crickets:
Racer Snake:
Swiftlets:
