El experimento del universo 25

(1) Considerable social turmoil among the 8 mice until they became adjusted to each other and to their expanded surroundings.
(2) Territories were established and nests were made.

Básicamente en esta fase lo que ocurrió es que los ratones se establecieron y se ajustaron al medio, se establecieron y se hicieron los nidos.

(1) Population doubling time is about 55 days
(1) Social organization established – frequency of litters proportional to social dominance
(1) The births tended to be concentrated in some sets of nest boxes (dominant males), while others (non-dominant males - withdrawn males = WM) had few or none.
(2) Although each living unit was identical in structure and opportunities, more food and water was consumed in certain areas. As the population increased, most mice associated eating and drinking with the presence of others. And crowding developed in certain units.
(1) At the end of this phase there were 3 times as many socially immature mice as there were socially established older ones.

Aquí en la segunda fase nos cuenta que la población se doblo en apenas 55 días. La organización social se estableció en una especie de jerarquización o dominación. En algunas áreas se consumía mas agua y comida que en otras (vaya que novedad).

Los nacimiento se concentraban en los nidos de los dominantes. Los ratones asociaban el comer y beber con la presencia de los otros. En algunas zonas se empezaban a apiñar. Y al final de la fase habia 3 veces mas ratones socialmente inmaduros de los que habian viejos y estabilizados.

Bastante curioso.

(1) Population doubling time is about 145 days
(1) The male ability to defend territory declines
(1) The nursing females become aggressive, essentailly 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.
(2) At this time, some unusual behaviour became noticeable. Violence became prevalent. Excess males strived for acceptance, were rejected and withdrew. Social disorder became visible – a WM would attack a passive WM, who in turn would attack another WM. Certain individuals became targets of repeated attacks. These individuals would have badly chewed and scarred tails.
(3) Socially withdrawn male 29 makes a pan-sexual approach to male 16 who he recently saw attacked. Note how one assumes the female role. Males exhibit sexual behaviour towards other males; you have rat homosexuality. They begin mounting the young.
(1) Incidence of conception decline and resorption of foetuses increases and dissolution of maternal behaviour is observed. This lead to non-reproducing females.
(1) By midway in phase C, essentially all young were prematurely rejected by their mothers. They started independent life without having developed adequate affective bonds.
(1) 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 were always opportunities for females to select an unoccupied space for rearing young if they so chose.
(1) Social disorder – a WM would attack a passive WM, who in turn would attack another.

Y creo que aquí empieza a pasar lo realmente interesante.

A pesar de estar en algunas zonas apiñados, la población volvió a doblarse en 155 días. La capacidad de los machos para defender el territorio se deterioro. Las hembras cuidadoras se volvieron agresivas, ocupando el rol de los machos de defender el territorio. Esto desencadeno que los jóvenes fueran atacados, heridos, y forzados a dejar la casa días antes de cuando era lo normal.

La violencia se volvió prevalente. Los machos rechazados se esforzaban en ser aceptados, para luego ser rechazados y apartados. Algunos desordenes sociales se volvían visibles tales como los machos rechazados atacaban a los machos rechazados pasivos y a su vez estos atacaban a otros. Algunos se volvían objeto de continuas agresiones (tenia las colas masticadas y cicatrizadas). Algunos machos se acercaban a los de las colas masticadas y estos asumían el rol de hembra. Aparecía comportamientos sexuales de machos hacia otros machos. Apareció la homosexualidad entre los ratones machos.

El descenso de la natalidad y el cambio del rol lleva a hembras no reproductivas. A mitad de esta fase todos los jovenes eran rechazados por sus madres. Empezaban a vivir vidas independientes sin el desarrollo de vinculos afectivos adecuados.

El 20% por ciento de los nidos estaban desocupados. A pesar de que las hembras podian elegir ocupar uno de estos para criar a sus crias, no lo hacian.

1) Population increase abruptly ceased on day 560 after colonization.
(1) Incidence of pregnancies decline very rapidly with no young surviving.
(1) The last conception took place about day 920
(1) Male counterparts to non-reproducing females were named the "beautiful ones". They never engaged in sexual approaches toward females, and they never engaged in fighting. Their behavioural repertoire became largely confined to eating, drinking, sleeping and grooming.
(1) The capacity for reproduction terminated.
(3) The last thousand animals born never learned to develop the social behaviours, they never learned to be aggressive, which is necessary in defence of home sites; not engaging in any stressful activity, and only paying attention to themselves, they groomed themselves well so they looked like very fine specimens.
(2) Other young mice growing into adulthood exhibited an even different type of behaviour. Dr Calhoun called these individuals "the beautiful ones". Their time was devoted solely to grooming, eating and sleeping. They never involved themselves with others, engaged in sex, nor would they fight. All appeared as a beautiful exhibit of the species with keen, alert eyes and a healthy well-kept body. These mice, however, could not cope with unusual stimuli. Though they looked inquisitive they were, in fact, very stupid.

Y llegamos al final.

El crecimiento de la población ceso abruptamente en el día 560 después de la colonización. La incidencia de embarazo bajo con nula supervivencia de los jóvenes. El ultimo nacimiento ocurrió el día 920. Aparecieron los que en el estudio llaman 'los guapos' ratones machos, la contraparte de las hembras que aparecieron en la fase anterior, no reproductivas, que se dedican a cultivar su cuerpo y no tienen relaciones sexuales, no se acercaban a las hembras ni participaban en las luchas, solo se centraban en comer, beber, dormir y crecer.

La capacidad de reproducción se acabo. Los últimos nacidos nunca aprendieron a desarrollar comportamiento sociales, no aprendían a ser agresivos para defenderse igualmente, igualmente solo se centraban en ellos, en crecer y en ser buenos especímenes.

Los últimos ratones jóvenes, eran como 'los guapos', atléticos, sanos, pero nunca interceptaron con los otros, no se reprodujeron, ni lucharon. Tenían un buen cuerpo, ojos en alerta, pero no respondían a los estímulos, diciendo el Dr. Calhoun que de hecho parecían muy estúpidos.