if the shelter is a public charity, the donations are deductible if you meet the substantiation requirements:
value less than $250 receipt and written records as to what was donated
value $250-$500 written acknowledgment from the charity and the same requirement as to your records
value $501 - $5,000 - same qs for $250-$400 + you must file form 8283
over $5,000 same as value $501 -$5,000 plus a qualified appraisal