The ornamental design for collar for animals, as shown and described.
1.1 is a front view of a collar for animals showing my new design;
1.2 is a left side view of the collar for animals;
1.3 is a top view of the collar for animals;
1.4 is a bottom view of the collar for animals;
1.5 is a first perspective view of the collar for animals;
1.6 is a second perspective view of the collar for animals; and
1.7 is a third perspective view of the collar for animals.
In the reproductions, the equal-length broken lines that show a leaf pattern depict portions of the collar for animals that form no part of the claimed design.