I wanted to know whether Law of Karma applies on animals/birds and other non-human creatures? Since all the animals(if not all), are dependent on other animals/creatures for food/living; how the law of Karma justified when these animals kill other animals? Is there anything specified in our Vedas in this regards? Please share the link, if possible.
Every being acts according to its own Guna and Swabhava and hence they are all subjected to law of Karma. Please refer to Manu Smriti.
In Verse 1.28-29, it says, all species of creatures have been allotted same kind of karmas that they were alloted in previous cycle of creation. Thus, species which were violent in previous creation are also violent in this etc.
1.30- it says, just as different seasons get their different characters naturally, similarly all animals develop Karmas suitable for them naturally.
1.41- says that Prajapatis have created all animals which are involved in their own karmas.
It gives more details from 1.42 verse onwards. More such references can easily be found.