E-toll tariffs will severely impact on the ability of the NSPCA to rescue animals, the organisation said on Tuesday.
"We do not receive any funds whatsoever from national or local government and exemption from Sanral [SA National Roads Agency Ltd] was denied," National Council of Societies for the Prevention of Cruelty to Animals (NSPCA) said in a statement.
Spokeswoman Christine Kuch said accidents involving animals, overturned trucks carrying animals or vehicles with animals on board involved in accidents, did occur.
The council appealed for exemption in September but this was denied.
It argued that the council was involved in "emergency issues" such as disasters, rescue missions, animal neglect and abuse investigations.
Kuch said rescuing and removing animals from highways was a means of effective accident prevention.
"The NSPCA now finds itself in a position whereby we shall have no option but to use public funds to pay for our vehicles to be allowed onto freeways as we go to assist animals," she said.
"It is ludicrous, if not downright immoral, that our hard-earned cash will be used for the purpose of paying tolls."
Sanral gazetted new tariffs on Friday. It described an "alternate user" as someone "who does not have a valid and operational e-tag, is not registered with Sanral, and who is not a day-pass user".
On Monday, Sanral said alternate users would be charged R1.75/km, compared to the standard tariff of 30c/km for registered users.
It said the higher fee was due to the need to recover costs, including invoicing and debt collection.
According to Sanral, 300,000 road users had bought e-tags at the beginning of April.
The toll system officially launches on April 30.
