The otters reside in the River Mydyr, which runs through Llanerchaeron estate
Otters might force the organisers of the Urdd eisteddfod into a re-think over where to park visitors' cars and caravans at next month's youth event.
Ceredigion council has deferred an application which could see land temporarily used for parking at the site near Aberaeron, Ceredigion.
There are concerns the move might have an impact on otters living in the nearby River Mydyr.
The eisteddfod runs from 31 May to 5 June at the Llanerchaeron estate.
The Urdd said it had been asked to cooperate with a survey into otter activity on the estate.
The festival's organisers want to park hundreds of cars and caravans on land there, near where the animals live.
The director of the Urdd eisteddfod, Aled Siôn, said: "As a result of the planning application submitted to Ceredigion County Council by the Urdd national eisteddfod, concerns were raised regarding otter activity in the River Mydyr on the Llanerchaeron Estate.
"A report has been commissioned and the Urdd national eisteddfod will adhere to any recommendations which follow.
"The Urdd national eisteddfod is often asked to adhere to guidelines to protect the natural environment when working on its maes [field] and staff and volunteers take this responsibility very seriously.
"The area in question relates to the car and caravan parks and does not directly affect the eisteddfod maes. These can be altered if the need arises and we're confident the festival will proceed as planned."
Mr Siôn added that work had already been carried out to protect some trees and some historical remains on the estate during the event.
The parking issue is the latest complication for organisers, who have agreed to sell alcohol at the youth festival for the first time.
The controversial move has raised objections from chapel leaders and concerns from the Children's Commissioner for Wales, Keith Towler.