The jaguar seems to prefer peccaries (javelina or skunk pig) although their diet reflects the abundance of whatever prey animal is available. There have been a number of studies which indicate that jaguars “have a particular fondness for peccaries” (the words of Fiona Sunquist in Wildcats of the World page 309). She is referring to A.S. Leopold and his book Wildlife of Mexico published in 1959 by Berkeley: University Of California Press.

The Essequibo Indians believe that the jaguar follows every heard of peccaries to pick up any animal who has strayed from the herd as easy prey when they are hungry.
A study in Peru supports this. In Manu National Park jaguars killed peccaries often and out of proportion to their abundance according to P.G. Crawshaw Jnr. in his work Comparative ecology of ocelot and Jaguar in a protected subtropical forest in Brazil and Argentina. This was his PhD dissertation from the University of Florida, Gainesville.
In Iguaçu National Park, Brazil white-lipped and collared peccaries are the favourite prey of jaguars. A major reason for their deaths is jaguar predation. And peccaries are also the most important prey animal for jaguars in Calakmul Biosphere Reserve, Mexico (source: J.M. Aranda 1992 – ask for the reference details if you are interested).

In the Venezuelan Llanos, jaguars selected out collared peccaries and capybaras while caimans and white-tailed deer were attacked and eaten less than expected based upon their availability (D. Scognamillo 2001).
Peccaries make quite a lot of noise through the rattling of their tusks. This sound has been described as “the clicking of a thousand pairs of castanets”. Their footsteps also make some noise as does their vocalisations. And, apparently, they are quite smelly. They have a strong acrid odour which hangs over the herd. These factors would seem to increase the chances of being attacked by a jaguar.
However, they are not a pushover as a prey animal because there are stories of peccaries attacking and sometimes even killing jaguars.