The concept is interesting and fun!

There are a few thing I found weird/unbalanced/missing regarding game design:

-You control the character with the keyboard, but you have to click on the animals to pick them, which means I have 2 things to keep track of. You should pick either full keyboard or full mouse gameplay, but both is weird.

-I wasn't able to NOT kill some animals. I mean, it's a game about saving them from a certain death, yet you have to make sacrifices at some point. I'd say either adjust the spawn rate/move speed of the animals to leave some room to cash in the boxes, or just auto-send the boxes.

-Regarding the death thing, I feel the game needs some sort of indicator, to know wether the animal is in danger or not.

-Putting the same animal in two different pens means having to sacrifice a whole species until you send the box, which I feel as too punishing. Maybe lock each pen to a species?

That was my random thoughts, feel free to take it in account or not :D I hope you had fun during the jam!

Happy game making, andhave a great day!