Feral Cats

About the Portsmouth Dockyard Study

The Portsmouth Dockyard authorities asked for someone to undertake a scientific study of the cats that lived there, mainly because of health concerns. When I started the study in October 1975, they had no idea of the size of the cat population, or of whether it was increasing or decreasing. They only knew that many dockyard workers were feeding the cats, while many others complained that the cats were a health hazard. After a visiting French Naval ship allowed its ship's dog to run loose in the dockyard, they became increasingly concerned about the risk of rabies entering the population.

At that time, the domestic cat was still considered to be a solitary animal, with the enduring image of Kipling's "cat that walked by himself". Despite the close association between cats and humans, little was known about the behaviour and ecology of free-living cats - in fact, more was known about the Serengeti Lion than about the feral cat in England.

As I studied this enclosed high-density population, I realised that the cats were living in social groups, and that much of their behaviour paralleled that of the lion, which was previously considered to be the only social cat.

I studied the cats by direct observation, recognising individuals primarily by coat pattern and assigning an identification number to each (you try thinking of that many names!). During the study, I gathered information on:

Habitat utilisation
Home range
Social behaviour
Population dynamics
Activity patterns
Coat colour genetics

I used this information to consider whether or not it was necessary to manage the population and, if so, how this might be achieved.

I published some of my results in a number of papers, but other information remained unpublished except in my PhD thesis. This site includes a brief summary of my research, together with PDF versions of four of my publications and some chapters of my PhD thesis.

Habitat utilisation

Portsmouth Dockyard is an enclosed area, its main walls having been built in 1711 and 1864. It includes basins and docks, and has a land area of about 85 ha. It is an urban habitat, with buildings, netted compounds, and a steam pipe system running in covered trenches. Plant life mainly occurs as small clumps or single plants. The animal life consists of insects such as cockroaches, birds (mainly gulls and pigeons) and mammals (mice and rats).

The total population of cats fluctuated around 300, and of adult cats fluctuated around 190. This gives an average density of over 2 cats per hectare, which is very high in comparison with rural populations (where it can be 1 cat per 8 hectares), and suggests a favourable environment.

The cats made use of a variety of abundant cover, as shown in the photographs. They were either fed by people, or foraged from skips and bins. I found only limited evidence of the natural food supply being utilised. The cats were generally well-fed.

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Home range

Not only did the dockyard cats have small home ranges, but the ranges of toms overlapped extensively, and females shared family group ranges.

Group range sizes were probably dependant on the resources available, and seemed to be independent of the number of cats in the group. Female cats usually spent most of their time in one small area, where there was food and shelter, and the number of times they ventured away from this 'core area' seemed to depend only on the temperament of the cat.

The ranges of the toms were about ten times the area of those of the females, and three times the length. The toms were usually seen at sites fairly evenly distributed through their ranges, although they tended to visit the core areas of several groups of females more frequently than other areas.

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Social behaviour

More information to follow - visit again soon!

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Population dynamics

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Activity patterns

I collected information on activity patterns during a few long periods of observation of two groups of cats, that covered the whole 24-hour cycle, in both winter and summer. This showed that the cats were not nocturnal, but tended to be active at dawn and dusk (crepuscular) and when when people were active. The cats spent 76 to 84% of their time largely inactive - comparable to the 85% recorded for the Serengeti lion by Schaller. But the extremely low level of activity (0.9%) of one young tom shows just how inactive a cat can be!

For detailed information, you can download the "Activity patterns" chapter from my thesis.

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Coat colour genetics

As a result of my article in the Feline Advisory Bureau Bulletin, I was contacted by two people working in field of cat coat colour genetics. I hadn't realised it, but for some years researchers had been "scoring" various cat populations for the frequency of various coat colour genes, and they were desperate to get their hands on detailed information on a sizeable colony recorded over a period of time.

More information to follow - visit again soon!

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