Olives live on sandy beaches and can easily be collected by beachcombing. Distribution data is scientifically useful.
There are about 150 species of olives, in four genera of the family Olividae, the genus Oliva - the true olives - has about 60 of these, with the rest belonging to the genera Ancillia, Olivancillaria, or Olivella.
Sand Burrowing Predators
All olives plough their way through tropical and sub-tropical sands in search of their prey. They can move very rapidly, faster than the bivalves they usually hunt, and certainly much more rapidly than the carrion that they will also eat! When they catch up with a bivalve (who can also burrow to get out of trouble) they drill a hole through one of the valves and squirt in digestive juices. They then suck up the dissolved nutrients (as opposed to the cone shells, who eat their prey whole and then spit out the tough bits).
Beachcombing
Because all of the cones live in sand the majority can be collected from the strand-line of sandy beaches. The shells will be in good condition at first (when first washed up), but wave-action will rapidly damage them. Collecting in this way is best done after violent weather, and in these conditions live animals may occasionally be thrown onto the beach, and since they move fast you will not have much time to grab them!.
Collecting Live Animals
When the tide is low it is possible to dig up patches of sand and pass it through a sieve. This will produce many bivalves and worms as well as the odd olive shell. Once captured these animals will need to be killed, cleaned and preserved before they can be displayed. (See ‘Collecting Mollusc Shells’.)
Recording Data
As with all shell collections, the value (both scientific and monetary) is increased if each shell is associated with the relevant data – where and when it was collected, the state of the tide and what the weather was like etc.. Since there is great variability among the olives it is also useful if a number of different colour varieties from the same population can be collected and displayed together (although this goes against the general rule of only taking one or two). Amateur collectors can really make a difference when it comes to detailed distribution of species and the different forms that occur in different places. Current distribution of any species needs to be known accurately before the effects of change (global warming, pollution, habitat loss etc.) can be assessed. Shell collectors are in a perfect position to help obtain this ‘base-line’ information, and serious hobbyists will publish their findings. (This is much easier now than it once was since there are numerous opportunities online. see discussion)
Main reference: Encyclopedia of Shells by S.Peter Dance (1974)
Other articles by John Blatchford
