Sorry, I have not tested that. When I go on vacation again I will test. I may not have time tomorrow though.
Only found out because I went on holiday with my pets and discovered the house did not have any Pet accessories so when buying Exploration gear I bought these as well.
I did some additional testing. It turns out that if you buy pet bowls at home and place them in your sims inventory then they are also thrown out. This leads me to believe that this is in fact an old bug that just surfaced now since before JA there was no reason to put them in the inventory. To see if it was there before it must be tested with a game that does not have the JA Game Pack.
Any time your Sim has a pet bowl in their inventory, if you click on that Sim, it will say: "Clean out spoiled food." If you do that they will pull out some "dirty dishes" scrape them into the trash and wash or throw away the "dirty dishes." The pet bowl will have disappeared from their inventory. Sims will autonomously preform these actions causing the pet bowl to disappear. It happens more often with the round pet bowls, but the squarish one is not immune.
I took 5 pets to the jungle, bought 5 pet bowls and my Sim immediately pulled out a pile of dirty dishes - pet bowls gone. She did not have the neat trait.
The only work around is to buy the bowls and travel immediately via the map to the trail head. Once you're in the jungle with no trash cans or sinks the opportunity to dispose of dirty dishes is limited.
I edited all the rentals to have pet feeders (and litter boxes).
I am still seeing this bug in new games. I took a pet dish with me to the Realm of Magic so that I can keep my cat familiar fed while I am using the magical facilities there. As @DizzyDee-K noted, the game treats the pet bowl like dirty dishes, and my Sim will throw it away. The "spoiled food" interaction appears regardless of whether the bowl is full or empty.
