The researchers theorised that either of the following situations could be antecedents to necrophilia:
The necrophiliac develops poor self-esteem, perhaps due in part to a significant loss;
(a) They are very fearful of rejection by others and they desire a sexual partner who is incapable of rejecting them; and/or
(b) They are fearful of the dead, and transform their fear—by means of reaction formation—into a desire. They develop an exciting fantasy of sex with a corpse, sometimes after exposure to a corpse. Motives
The most common motive for necrophiliacs is the possession of a partner who is unable to resist or reject them. However, in the past, necrophiliacs have expressed having more than one motive.The authors reported that of their sample of 34 genuine necrophiliacs:
68% were motivated by a desire for a non-resisting and non-rejecting partner
21% were motivated by a want for a reunion with a lost partner
15% were motivated by sexual attraction to dead people
15% were motivated by a desire for comfort or to overcome feelings of isolation
12% were motivated by a desire to remedy low self-esteem by expressing power over a corpseLesser common motives include:

Unavailability of a living partner
Compensation for a fear of women
Belief that sex with a living woman is a mortal sin
Need to achieve a feeling of total control over a sexual partner
Compliance with a command hallucination
Performance of a series of destructive acts
Expression of polymorphous perverse sexual desires
Need to perform limitless sexual activityIQ data was limited, but not abnormally low. About half of the sample had a personality disorder, and 11% of true necrophiliacs were psychotic.
"When one died the other one just went for it and didnt get any negative feedback – well, didnt get any feedback," according to Moeliker. Necrophilia had previously only been reported in heterosexual mallard pairs.In a short paper known as "Sexual Habits of the Adélie Penguin", deemed too shocking for contemporary publication, George Murray Levick described "little hooligan bands" of penguins mating with dead females in the Cape Adare rookery, the largest group of Adélie penguins, in 1911 and 1912. This is nowadays ascribed to lack of experience of young penguins; a dead female, with eyes half-closed, closely resembles a compliant female. A gentoo penguin was observed attempting to have intercourse with a dead penguin in 1921.A male New Zealand sea lion was once observed attempting to copulate with a dead female New Zealand fur seal in the wild. The sea lion nudged the seal repeatedly, then mounted her and made several pelvic thrusts. Approximately ten minutes later, the sea lion became disturbed by the researchers presence, dragged the corpse of the seal into the water, and swam away while holding it. A male sea otter was observed holding a female sea otter underwater until she drowned before repeatedly copulating with her carcass. Several months later, the same sea otter was again observed copulating with the carcass of a different female.