"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.
When his attempts failed, and his male victim died, he would keep the corpse until it decomposed beyond recognition,  masturbating and performing sexual intercourse on the body. He would perform sexual activities before and after murdering his victims. Dahmer explained that he only killed his victims because he did not want them to leave. More modern necrophiliacs include Scottish serial killer Dennis Nilsen, and English David Fuller, who is considered the worst offender of this kind in English legal history.Havelock Ellis, in his 1903 volume of Studies of the Psychology of Sex, believed that necrophilia was related to algolagnia, in that both involve the transformation of a supposed negative emotion, such as anger, fear, disgust, or grief, into sexual desire. Classification
In the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), recurrent, intense sexual interest in corpses can be diagnosed under Other Specified Paraphilic Disorder (necrophilia) when it causes marked distress or impairment in important areas of functioning.Forensic Psychologist Anil Aggrawal introduced a ten tier classification of necrophiliacs based on increasing severity of disorder. Additionally, criminologist Lee Mellors typology of homicidal necrophiliacs consists of eight categories (A–H) and is based on the combination of two behavioural axes: destructive (offender mutilates the corpse for sexual reasons) – preservative (offender does not), and cold (offender used the corpse sexually two hours or more after death) – warm (offender used the corpse sexually less than two hours after death). This renders four categories (A-D) to which Mellor adds an additional four (E-H):

Category A (cold/destructive), e.g.