Habitat saturation, due to high population density, and predation pressure have
both demonstrated to influence the formation of some social systems. For example,
helper-at-the-nest systems are formed when offspring delay dispersal due to a
lack of suitable territory availability or high cost of dispersal. In one cooperative
avian species, the pukeko (Porphyrio melanotus melanotus), a previous comparison
between high density (North Island) and low density (South Island) populations
found that at high density, there were fewer dispersal opportunities due to habitat
saturation resulting in increased relatedness amongst group members. Climatic
variations between the North Island and the South Island could explain many of
the results previously found. The recent decimation of a large pukeko population
at a North Island site provided us with a unique opportunity to compare group
structure between two populations under similar climatic conditions to determine
whether or not individuals bred independently in a low density population. For my
thesis I aimed to answer three questions. First, how does population density affect
the dispersal of offspring from their natal territory? Second, how does population
density affect relatedness of adult group members? Third, how does density affect
territory size? In this thesis I was unable to determine whether or not dispersal
events were occurring or if there was high or low relatedness amongst group
members. Territory sizes were significantly smaller at Tawharanui over Shakespear
but they were not significantly correlated with group size. Harrier presence was
significantly different between paddocks. / Thesis / Master of Science (MSc) / Ecological constraints have been shown to influence the formation of social
groups. The decimation of a population of cooperatively breeding pukeko on the
North Island of New Zealand provided us with a unique opportunity to compare
two populations under different density conditions. I explored the effect of population
density on group composition, parentage, and territory size as a means
to understand the costs and benefits of cooperative breeding and joint-nesting.
Territory sizes were significantly larger under low density conditions. I was unable
to determine whether or not population density influenced offspring dispersal or
relatedness amongst group members.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21243 |
| Date | January 2017 |
| Creators | Healey, Meghan |
| Contributors | Quinn, Jim, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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