No, with increasing oil prices and the environmental concerns of hydrocarbon based plastic biodegradability in the last decades there was a trend toward bioplastic that is made from bones and food wastes. Some companies like Martin use these materials and advertise that their ukes are biodegradable. So a plastic uke may even contain more dead animal than a wooden uke.
Other animal parts often used even on cheap ukes are seashell parts for decorative inlay and fret markers. Bling is usually a good indicator for considerable dead animal content.