Organisers say numbers have doubled for this year's Durrell Dash.
More than 500 people are expected to take part in the fundraising event on the morning of Sunday 16 October.
There is a 13km (8 mile) rave and, for the first time, a 6km (3.72 mile) race. Both start and finish at the Durrell Wildlife Park in Trinity.
Durrell's events co-ordinator, Andrew Scott-Miller, said the event had already made £5,000 through entry fees alone.
He said he was concerned as two weeks ago the event had only had 20 entries, but he said they had since come flooding in.
The money raised at the event goes to the conservation charity to help in its mission to save species from extinction.