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Introduction to Death Squared

by Ed Coll 5-15-96

Living on an island like Kauai my thoughts often wander to questions of sustainability, quality of life, and carrying capacity. When Captain Cook came to Kauai there where an estimated 50,000 Native Hawaiians living on Kauai. That's about the population of Kauai today. But there is a difference. Today, Kauai's 50,000 residents are 85% dependent on imports. My definition of "carrying capacity" for Kauai is the number of people this island can support on a sustainable basis without the importation of goods.

"We can't alter our lifestyle and go back to living in grass shacks. We've got to be good consumers to keep the GNP rolling", an anonymous source says.

Well, what's the alternative?

What if Kauai was a true Paradise with all our housing, food, and water provided for us in abundance? What if more and more people moved to Kauai? At what point would the population density turn Paradise into a living Hell?

Death Squared is the story of a paradise for mice called Universe 25. All the needs of the mice were provides for (shelter, food, water, etc.). Four pairs of mice colonized Universe 25 and began breeding. The population increased with some interesting results regarding survival. This is not a science fiction story but a real scientific study. Is there a lesson for humankind in this tale of mice?

Read on but please keep in mind this mantra: "People aren't mice. We can adapt."

Can we?

Death Squared:

The Explosive Growth and Demise of a Mouse Population

by John B Calhoun MD
(Section on Behavioral Systems,
Laboratory of Brain Evolution & Behavior,
National Institute of Mental Health,
9000 Rockville pike,
Bethesda, Maryland 20014, USA)

Fig 1 Universe 25, February 10,1970, 681 days after colonization. Calhoun in universe with an exceptionally large aggregate of pooled withdrawn mice on the floor just across the centre of the floor from him. Note the aggregation of mice on some food hoppers in contrast to their near absence on others. This is the 'behavioural sink' phenomenon in which the learned need for proximity to others as a secondary reinforcer at a resource site gains dominance over the primary need, in this case food.

- Photo by Yoichi R Okamoto -

I shall largely speak of mice, but my thoughts are on man, on healing, on life and its evolution. Threatening life and evolution are the two death: death of the spirit and death of the body. Evolution, in terms of ancient wisdom, is the acquisition of access to the tree of life. This takes us back to the white first horse of the Apocalypse which with its rider set out to conquer the forces that threaten the spirit with death. Fourth: in Revelations (liabilities) we note: 'To him who conquers I will grant to eat the tree of life, which is in the paradise of God' and further on (Rev. xxii.2): 'The leaves of the tree were for the healing of nations.'

This takes us to the fourth horse of the Apocalypse (Rev. vi.7): 'I saw... a pale horse, and its rider's name was Death, and Hades followed him; and they were given power over a fourth of the earth, to kill with the sword and with famine and with pestilence and by wild beasts of the earth' (italics mine). This second death has gradually become the predominant concern of modern medicine. And yet there is nothing in the earlier history of medicine, or in the precepts embodied in the Hippocratic Oath, that precludes medicine from being equally concerned with healing the spirit, and healing nations, as with healing the body. Perhaps we might do well to reflect upon another of John's transcriptions (Rev. ii.ll): 'He who conquers shall not be hurt by the second death.'

Bodily Mortality

Let us first consider the second death Table I). The four mortality factors listed in Revelation have direct counterparts (with a division of one of them to form a total of five) in the ecology of animals in nature. I shall briefly treat each of these five mortality factors, and then discuss the steps taken to eliminate, or drastically reduce, the impact of each in a Utopian
environment constructed for mice.

(1) Emigration: Animals in the wild rarely die from the 'sword' directly; few are the deaths from intraspecific combat Rather it is that individuals, who have failed in the more symbolic conflicts involved in gaining the right to remain in the locality of their birth or in more preferred habitats, take recourse to movement into peripheral unoccupied or suboptimal habitats In strange and less favourable habitats the emigres become more exposed to other mortality factors. Any removal of excess members from an established population, from the point of view of change in its numbers, represents mortality.In this sense emigration is a mortality factor.

(2a) Resource shortage: classically food and water have received the focus of attention with respect to their reduction increasing the likelihood of death. Shortages of shelter, other environmental resources and associates lead to debilitation, and an unsatisfactoriness of habitat that culminate in death or failure to reproduce (species death).

(2b.) Inclement weather: Every species of animal has developed a genetic adaptation to some particular range of external conditions which affect its physiology. Any conditions of wind, rain, humidity or temperature which exceed the usual limits of tolerance bring death immediately or increase the risk of death through debilitation. Beyond these more usual contributions to mortality, flood and fire represent cataclysmic changes that have widespread and more long-lasting effects on population numbers.

(3) Disease: Although most animals develop some capacity to tolerate the parasites, bacteria and viruses that invade their bodies, most species still remain subject to epidemic decimation in addition to a more normal attrition from disease. Abnormally high densities enhance the likelihood of spread of disease to epidemic proportions.

(4) Predation: Practically every species has, through evolution, had associated with it predators capable of killing some of its members.

Despite loss of members from these five kinds of mortality, most species persist over long Periods, even those measured in geological time. To do so every such species has developed capacities for reproduction requisite to compensate for losses from the normal impact of mortality factors other than ageing. I have omitted senescence as a mortality factor since rare is the animal who lives long enough in nature to reach a post-reproductive age without having succumbed to one of the above mortality factors.

A Mortality-inhibiting Environment for Mice

Some of the attributes of this environment have been discussed or figured elsewhere (Calhoun 1969, 1971, Wigotsky 1970). Here I shall describe how its design reduced mortality.

(1) Emigration prevention: A closed physical universe was formed by four 54 inch (1.37 m) high walls forming a square of side 101 inches (2.57 m). Although the walls were structured for use by mice to increase the effective use-area of the universe, the mice could not climb over the upper 17 inch (43 cm) unstructured portion of the galvanized metal walls.

(2a) Resource supra-availability: Each 25* inch (64 cm) linear segment of wall was identically structured. Four 3 inch (7.6 cm) diameter tunnels 34 inches (86 cm) long of j inch (12.5 mm) mesh wire were soldered vertically to the walls. The open lower end, just above the floor which was covered with ground corn cob, gave access to each tunnel. At 8 inch (20.3 cm) intervals above the floor in each tunnel four 1 * inch (3.2 cm) openings through the tunnel mesh and the metal wall gave access to 8x5x4 inch (20.3x12.7x 10.2 cm) retreat nesting boxes. Fifteen mice could comfortably rest in a single nest box.

Thus there were four
four-unit walk-up
one-room apartments
in each cell.

Thus there were four four-unit walk-up one-room apartments in each cell. The cell is the replicated wall configuration, here being described, with an associated 640 sq. inch (0.356 m2) of floor space. A wire mesh food hopper with a 6 x 10 inch (15x25 cm) surface was located in each of the 16 cells halfway up the wall and in contact with the right-hand tunnel of each set of four tunnels. Mice climbing across the outer surface of the tunnel gained access to the food hopper. Twenty five mice could feed simultaneously on a hopper. By further climbing up the outside surface of the tunnels mice had access to a 4x18 inch (10x45 cm) platform above which four water bottles were suspended. Two mice could drink simultaneously at each bottle. An abundant supply of paper strips for nesting material was always available on the floor a few inches out from the bases of the tunnels. Considering the time required to eat and drink, access to food would not have been a limiting variable until a population of 9500 was reached, or 6144 for water. Considering that there were 256 nest retreat sites in the 16 cells one would not expect shelter to be a limiting factor until the population exceeded 3840. Due to the tendency of many animals to choose to crowd together in numbers in excess of 15 per nest site, at the peak population size of 2200 mice, 20% of all nest sites were usually unoccupied. Thus there was always opportunity for females to select an unoccupied space for rearing young if they so chose.

(2b) Weather amelioration: The mouse universe was located on the second floor of a prefabricated metal building. During the cooler months of the year ambient temperature was kept close to 68F (20C) During the warmer months of the year large exhaust fans kept ambient temperatures mostly within the 70-90F (21-32C) range of the outside environment. Being indoors, rain could not contribute to debilitation. Air movement was kept low, except when this favoured heat loss during periods of higher ambient temperature. No evidence was ever obtained to indicate that such weather conditions enhanced mortality.

(3) Disease control: The Balb C albino house mice (Mus musculus) used as colonizers in this study were obtained from the National Institutes of Health breeding colony where extreme precautions are followed to preclude establishment of epidemic type diseases such as salmonella. Bacterial culture taken at the highest density of the population indicated that such organisms were not a factor in our study. About every four to eight weeks the ground corn cob in all nest boxes and the floor. was removed along with accumulated feces.

(4) Predation: No predators were present.

Some mortality did occur throughout the history of the population we initiated in this 16 cell universe. Not until the mice became quite old did the mortality from ageing contribute significantly to removal of members from the population. On the basis of initial analyses, menopause in females comes at about 560 days of age. Although we have not yet determined the average life expectancy at weaning, I suspect that it is well past menopause. Large numbers of mice lived to 800 days of age, which is equivalent to 80 years of age for a human.

Explosive Initial Population Growth, the Resource Exploitation Phase B

Four pairs of 48-day-old Balb C strain house mice were introduced into the 16 cell universe on July 9 1968, after each mouse had been isolated for 21 days following weaning. There followed a period of 104 days (Phase A) before the first litters were born. These 104 days were marked by considerable social turmoil among these 8 mice until they became adjusted to each other and to their expanded surroundings. Following this adjustment and the birth of the first litters the population exhibited an exponential increase, with a doubling time of about 55 days (Fig 2). This progression of numbers was approximately 20, 40, 80, 160, 320, to 620 after nearly five doublings. I call this period of most rapid growth Phase B. At 620 weaned mice the rate of population growth abruptly decreased to a doubling time of approximately 145 days. Periodically through Phase B, young born into the universe reached sexual maturity and bore young, thus contributing to the compound interest rate of population growth.

Distribution of place of birth (Fig 3) of mice born during Phase B provides an insight into the social organization that developed. The square represents the wall of the pen, and the small black rectangles depict the locations of the food hoppers along its inner surface. Between each two hoppers there are four sets of walk-up apartments, each set containing four nest boxes accessible by a single tunnel. The total young born in each of the 64 sets of four nest boxes were tabulated for the period through the first survey after the termination of Phase B. These totals are shown in Fig 3 as open bars extending outward from the wall of the pen.

It may be seen that births tended to be concentrated in some sets of nest boxes, while others had few or none. This uneven distribution of births reflects a clustering of reproducing females into brood groups defined in Fig 3 by lines radiating toward the centre of the universe from the bases of nest boxes at the interface between each two adjoining brood groups. Total births per brood group are indicated between radial lines. These totals reflect two properties of a closed social system:

(1) Bilateral symmetry: The northeast brood group produced only 13 young in 252 days whereas the opposite southwest brood group produced over eight times as many, 111. Between these two extremes from the location of the peak producing brood group toward the least productive one, in both clockwise and counterclockwise directions, there is a decline in number of young born. This trend reflects the attempt by the members of the population to superimpose a more effective bilateral symmetry of organization upon an environment that tends toward radial symmetry.

(2) Hierarchy of groups: Productivity of a group may be taken as an index of its social status. The fourteen brood groups may thus be ranked with rank No.1 assigned to the group which produced 111 young, and rank No.14 to the one which produced only 13 young. Plotting the number of young produced as a function of this ranking (Fig 4) reflects a remarkable
hierarchical ordering within the total social system. This type of ordering is identical to that which results when we examine the degree of activity exhibited by the several males of an interacting group. The most dominant male is the most active one, and as social dominance decilnes so does the degree of activity. Such activity is termed 'social velocity' (Calhoun 1963, 1967, 1971). Our studies show that in a group of 14 males social velocity declines linearly with rank with approximately the same slope as in Fig 4. Each of the brood groups had associated with it a male which was territorially dominant within an area on the floor roughly coinciding with the sectors shown in Fig 3. All the ranges of these territorial males overlapped near the centre of the universe The most dominant male was always associated with the brood group that produced the most young, and the degree of dominance of the other territorial males tended to be reflected by the productivity of females associated with them.

Both bilateral and hierarchical social organization during Phase B contributed to a maximum exploitation of resources that led to an explosive rate of increase of the population. At the end of this phase all the most desirable physical space was filled with organized social groups. These 14 social groups totalled 150 adults. On average each group contained over 10 individuals including a territorial male, associated males and females and their juvenile and subadult progeny. At the end of Phase B there were 470 of these immature mice that had experienced good maternal care and early socialization. Thus there were over three times as many younger animals as the socially established older ones. This number is far greater than would have existed had the normal ecological mortality factors functioned.

Inhibited Secondary Population Growth, the Stagnation Phase C

Beginning at Day 315 after colonization and continuing for 245 more days, the population grew at a much slower rate, doubling only every 145 days rather than each 55 days as in Phase B. let us examine the circumstances surrounding this decline in rate of population growth. In the normal course of events in a natural ecological setting somewhat more young survive to maturity than are necessary to replace their dying or senescent established associates. The excess that find no social niches emigrate. However, in my experimental universe there was no opportunity for emigration. As the unusually large number of young gained adulthood they had to remain, and they did contest for roles in the filled social system. Males who failed withdrew physically and psychologically; they became very inactive and aggregated in large pools near the centre of the floor of the universe. From this point on they no longer initiated interaction with their established associates, nor did their behaviour elicit attack by territorial males. Even so, they became characterized by many wounds and much scar tissue as a result of attacks by other withdrawn males. Return of 2 or more males, who had gone to eat and drink, marked an abrupt shift in the level of ambient stimuli for their quiescent associates. Resultant excitation often precipitated one of the resting males into an attack upon his other withdrawn associates who, having lost the capacity for fleeing remained relatively immobile despite receiving vicious attacks. A mouse so attacked would at a later time become an attacker. Female counterparts of these withdrawn males tended to withdraw to higher level boxes that were less preferred by females with litters. Such females were not characterized by the violent aggression of the withdrawn males.

As a result of the extreme demands made on territorial males to reject maturing associates, their ability to continue territorial defence decline. Gradually the frequency of this involvement in territorial defence declined as did the area defended. This left nursing females more exposed to invasion of their nest sites. Normally nursing females in the presence of territorial males exhibit little aggression. However, in response to invasion of nest sites and bases of ramps leading to them, the nursing females did become aggressive, essentially taking over the role of the territorial males. This aggression generalized to their own young who were attacked, wounded, and forced to leave home several days before normal weaning. During Phase C the incidence of conception declined, and resorption of foetuses increased. Maternal behaviour also became disrupted. Young were often wounded in the delivery process. Females transported their young to several sites, during which processsome were abandoned. Many litters of a young age on one survey disappeared before the next survey. Such abandoning of young following survey disturbance is a particularly sensitive index of dissolution of maternal behaviour. The combined effect of these several factors affecting reduced conception, increased fetal mortality and increased preweaning mortality largely accounts for the abrupt decline in rate of population growth characterizing Phase C. For all practical purposes there had been a death of societal organization by the end of Phase C.

Decline of Population Size, the Death Phase D

Population increase abruptly cased on Day 560 after colonization. A few mice born up until Day 600 survived past weaning. Between these times deaths just slightly exceeded births. Beyond the time of the last surviving birth on Day 600 the incidence of pregnancies declined very rapidly with no young surviving. Last conception was about Day 920. With the increase in rate of mortality accompanying senescence, the population has continued to decline in numbers. By March 1 1972, the average age of survivors was 776 days, over 200 days beyond menopause.

The last surviving male will
be dead on May 23 1973,
1780 days after colonization.

On June 22 1972, there were only 122 (22 male, 100 female) survivors. Projection of the prior few months of exponential decline in numbers indicates that the last surviving male will be dead on May 23 1973, 1780 days after colonization. The population will be, reproductively, definitely dead at that time, although such death was predicted by 700 days after colonization. This demise of a population contradicts prior knowledge which indicates that when a population declines to a few remnant groups, some individuals will reinitiate its growth.

Turning back to the end of phase C, the seeds for eventual destruction may already be seen to have been sown. By midway in Phase C essentially all young were prematurely rejected by their mothers. They started independent life without having developed adequate affective bonds. Then as they moved out into an already dense population many attempts to engage in social interaction were mechanically disrupted by passage of other mice. Lastly, I have shown (Calhoun 1963) that in proportion to the extent that the group size exceeds the optimum, maximizing gratification from such interactions necessitates a decrease in the intensity and duration of such behaviours. This fragments otherwise more complex behaviours. As a result of these three processes (failure to develop early social bonding, mechanical interference with developing social behaviours and fragmentation of behaviours) maturation of the more complex social behaviours such as those involved in courtship, maternality and aggression failed. For females a clear example may be taken from a 2 cell universe studied in parallel with the 16 cell one detailed here. The members of this population were killed 300 days after the inflection point of the shift from Phase C to Phase D. Among these were 148 females born within the last 50 days before the end of Phase C. At autopsy at a median age of 334 days only I 8% had ever conceived (i.e. no placental scars in the uteri of 82% of the females) and only 2% were pregnant (each of these 3 females had only one embryo as contrasted to the more normal S or more). By this age most females in a normal population would have had five or more litters, most of them successfully reared.

Male counterparts to these
non-reproducing females
we soon dubbed the
'beautiful ones'.

Male counterparts to these non-reproducing females we soon dubbed the 'beautiful ones'. They never engaged in sexual approaches toward females, and they never engaged in fighting, and so they had no wound or scar tissue. Thus their pelage remained in excellent ,condition. Their behavioural repertoire became largely confined to eating, drinking, sleeping and grooming, none of which carried any social implications beyond that represented by contiguity of bodies.

Most of the last half of the population born in the 16 cell universe were fully or largely like these non-reproducing females and these 'beautiful ones' (males). As their formerly more competent predessors gradually became senescent, their already disrupted capacity for reproduction terminated. At this time only the 'beautiful one' category of males, and their counterpart females, remained at an age normally compatible with reproduction, but they had long since failed to develop this capacity.

My colleague, Dr. Halsey Marsden (1972), conducted several studies during the mid-third of Phase D in which he placed small groups of mice out of these crowded populations into new universes at very low densities. All groups exhibited nearly total loss of capacity for developing a structured society or for engaging in the full repertoire of reproductive behaviours. Even placing them with adequate sex partners of the opposite sex, that had matured in uncrowded conditions, also gave very little indication of retention of any adequate reproductive behaviour.


The results obtained in this study should he obtained when customary causes of mortalitv become markedly reduced in any species of mammal whose members form social groups. Reduction of bodily death (i.e. 'the second death') culminates in survival of an excessive number of individuals that have developed the potentiality for occupying the social roles characteristic of the species. Within a few generations all such roles in all physical space available to the species are filled. At this time, the continuing high survival of many individuals to sexual and behavioural maturity culminates in the presence of many young adults capable of involvement in appropriate species-specific activities. However, there are few opportunities for fulifiling these potentialities. In seeking such fulfilment they compete for social role occupancy with the older established members of the comrmunity. This competition is so severe that it simultaneously leads to the nearly total breakdown of all normal behaviour by both the contestors and the established adults of both sexes. Normal social organization (i.e. 'the establishment') breaks down, it 'dies'.

Young born during such social dissolution are rejected by their mothers and other adult associates. This early failure of social bonding becomes compounded by interruption of-action cycles due to the mechanical interference resulting from the high contact rate among individuals living in a high density population. High contact rate further fragments behaviour as a result of the stochastics of social interactions which demand that, in order to maximize gratification from social interaction, intensity and duration of social interaction must be reduced in proportion to the degree that the group size exceeds the optimum. Autistic-like creatures, capable only of the most simple behaviours compatible with physiological survival, emerge out of this process. Their spirit has died ('the first death'). They are no longer capable of executing the more complex behaviours compatible with species survival. The species in such settings die.

For an animal so complex as man, there
is no logical reason why a comparable
sequence of events should not also
lead to species extinction.

For an animal so simple as a mouse, the most complex behaviours involve the interrelated set of courtship, maternal care, territorial defence and hierarchical intragroup and intergroup social organization. When behaviours related to these functions fail to mature, there is no development of social organization and no reproduction. As in the case of my study reported above, all members of the population will age and eventually die. The species will die out.

For an animal so complex as man, there is no logical reason why a comparable sequence of events should not also lead to species extinction. If opportunities for role fulfilment fall far short of the demand by those capable of filling roles, and having expectations to do so, only violence and disruption of social organization can follow. Individuals born under these circumstances will be so out of touch with reality as to be incapable even of alienation. Their most complex behaviours will become fragmented. Acquisition, creation and utilization of ideas appropriate for life in a post-industrial cultural-conceptual-technological society will have been blocked. Just as biological generativity in the mouse involves this species most complex behaviours, so does ideational generativity for man. Loss of these respective complex behaviours means death of the species.

Mortality, bodily death = the second death
Drastic reduction of mortality
= death of the second death
= death squared
(Death)2 eads to dissolution of social organization
=death of the establishment
Death of the establishment leads to spiritual death =loss of capacity to
engage in behaviours essential to species survival
=the first death
(Death)2=the first death.

Happy is the man who finds wisdom, and the man who gains understanding.
Wisdom is a tree of life to those who lay hold of her.
All her paths lead to peace. (Proverbs iii.13, 18 and 17, rearranged)

Calhoun J B
(19,63) In: Physiological Mammalogy. Ed. W Mayer &
Ryan Gelder. Academic Press. New York; 1, I-I 117
(1967) In: Comparative Psychopathology. Ed. J Zubin.
Grune &Sirattoe,, New York; pp 1-51
(1969) Architectural Association Quarterly 1, No.3, 24-35
(1971) In: Behavior and Environment - The Use of Space:ace by
Animals and Men. Ed. A H Esser. Plenum, New York; pp 329-3117
Maruden H M (1972) In: Environment and the social Sciences:
Perspectives and Applications. Ed. J F Wohwill & D H Carson.
American Psychological Association, Washington, DC; pp 5-14
Marsden H M ,Calhoun J B & Ng LKY
(1971) Crowding and Maladaptation: Behavioral and
Neurochemical Observations. (Paper presented at the
Annual Meeting of the American Association for the
Advancement of Sciences, Philadelphia, December 1971
Wigotsky Y W (1970) In: Engineering and the
Urban Crisis: Part 3. Urban Congestion,
Design News, Cahners, Denver, Col.; September 15, pp 48-60

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