Here’s an ethical issue and Jewish source response:

Case

Ruthie is passing by a street when a cat with a collar (indicating it has an owner) follows her.  She wants to pick it up and return it to its owner, but immediately realizes that it will take a lot of time, effort and money to give back this cat.  After all, in addition to the time it will take to care for her, Ruthie will have to feed her and pay for ads to let people know where the cat is.  

Answer

The question is about the obligation to return lost objects found on the street which would occupy much time and some expense.  

[a] In most societies, no one expects or requires anyone to pick up such an object.  If one does so it is viewed as so extraordinary that the returner expects a reward.  In Judaism, though, the returning of a lost object is mandatory, and a person is guilty of a sin if he or she merely passes by a lost object without retrieving it.  The Torah emphasizes this when it says “You shall not watch your neighbor’s ox or his sheep go astray, and hide yourself from them; you shall in any case bring them again to your neighbor.  And if your neighbor is not near you, or if you do not know your neighbor, then you shall bring it to your own house, and it shall be with you until your neighbor seeks it, and you shall return it.  In like manner shall you do with a donkey; and so shall you do with a garment; and with every lost thing of your neighbor’s, which that has been lost and you have found, you may not hide yourself from this responsibility.” (Deuteronomy 22:1-3) 

Since the verse specifically speaks about the return of lost animals, Ruthie would have to return the cat, especially since the collar is an identifying sign for the owner.  If there is no identifying sign, including the location in which the animal was found, then the finder can keep it since we assume the owner gave up all hope of retrieving such an object or animal (Shulchan Aruch, Choshen Mishpat 259:2).

[b] What about Ruthie’s expenses?  Of course the finder can later charge the owner for expenses such as feeding the animal (Shulchan Aruch, Choshen Mishpat 265:1).  Similarly, should Ruthie need to take time off work to find the owner, these expenses can also be recovered (Shulchan Aruch, Choshen Mishpat 265:1).  If the expenses become greater than the worth of the object, then (and only then) would the finder not be obligated to retain the object and try to return it.  

Joel Grishaver, “You Be the Judge 2”, pgs. 47-48

Used with permission from Joel Grishaver