title: Sub-Optimal Choice Behaviour by Possums

authors: Hancox, Victoria Leigh

abstract: This study aimed to investigate sub-optimal choice using six brushtail possums (Trichosurus vulpecula.).  Experiment 1 replicated Zentall and Stagner’s (2011) procedure where the possums were required to choose between two alternating alternatives; The low probability alternative (sub-optimal) was a discriminative stimuli signalling 3.5-s reinforcement on 20% of the trials, and non-reinforcement on 80% of the trials; the high probability alternative (optimal) was a non-discriminative stimuli signalling 1-s reinforcement 100% of the time regardless of the stimulus presented.  This was unsuccessful as the possums showed a clear indifference to the alternatives.
  Due to these ambiguous results, we replicated two conditions of Stagner and Zentall’s (2010) procedures to achieve sub-optimal responding in possums. Experiment 2 was similar to Experiment 1, however the alternation was removed and the high probability alternative was a non-discriminative stimuli associated with 50% reinforcement regardless of the stimulus presented.  Sub-optimal responding was not achieved, however the possums now showed a preference for the optimal alternative.
   Alternation may have affected Experiment 1 and to examine this theory, Experiment 3 was replicated without alternation. Interestingly, we found a preference for the high probability alternative. Experiment 4 replicated Experiment 3; however the length of time for reinforcement was altered to attenuate sub-optimal responding. A preference for the high probability alternative which provided an overall greater net payoff was found. The possums changed from indifference to choosing optimally. It appears that possums do not have a preference for the sub-optimal choice the same as pigeons.

text: Sub-Optimal Choice Behaviour by Possums This study aimed to investigate sub-optimal choice using six brushtail possums (Trichosurus vulpecula.).  Experiment 1 replicated Zentall and Stagner’s (2011) procedure where the possums were required to choose between two alternating alternatives; The low probability alternative (sub-optimal) was a discriminative stimuli signalling 3.5-s reinforcement on 20% of the trials, and non-reinforcement on 80% of the trials; the high probability alternative (optimal) was a non-discriminative stimuli signalling 1-s reinforcement 100% of the time regardless of the stimulus presented.  This was unsuccessful as the possums showed a clear indifference to the alternatives.
  Due to these ambiguous results, we replicated two conditions of Stagner and Zentall’s (2010) procedures to achieve sub-optimal responding in possums. Experiment 2 was similar to Experiment 1, however the alternation was removed and the high probability alternative was a non-discriminative stimuli associated with 50% reinforcement regardless of the stimulus presented.  Sub-optimal responding was not achieved, however the possums now showed a preference for the optimal alternative.
   Alternation may have affected Experiment 1 and to examine this theory, Experiment 3 was replicated without alternation. Interestingly, we found a preference for the high probability alternative. Experiment 4 replicated Experiment 3; however the length of time for reinforcement was altered to attenuate sub-optimal responding. A preference for the high probability alternative which provided an overall greater net payoff was found. The possums changed from indifference to choosing optimally. It appears that possums do not have a preference for the sub-optimal choice the same as pigeons.

year: 2016

title: Rationale and methodology for a national study of higher education science and engineering learning communities

authors: Coll, Richard K.

subjects: high education

abstract: This paper reports on a major national study of higher education science and engineering learning communities in New Zealand. The scope of the research project along with a description of the methodology and method used in the study together with rationale for the study and research approach adopted are provided here. Details of the theoretical framework and a discussion of paradigm that underpinned the study are presented. A discussion of issues of reliability and validity and measures taken to maximize these also is presented. The paper begins with an overview of the New Zealand compulsory education sector and traces the now multitudinous pathways into higher education nationally. It thus provides a valuable context for this national study of higher education science and engineering learning communities.

text: Rationale and methodology for a national study of higher education science and engineering learning communities This paper reports on a major national study of higher education science and engineering learning communities in New Zealand. The scope of the research project along with a description of the methodology and method used in the study together with rationale for the study and research approach adopted are provided here. Details of the theoretical framework and a discussion of paradigm that underpinned the study are presented. A discussion of issues of reliability and validity and measures taken to maximize these also is presented. The paper begins with an overview of the New Zealand compulsory education sector and traces the now multitudinous pathways into higher education nationally. It thus provides a valuable context for this national study of higher education science and engineering learning communities.

year: 2008

title: Mai uta ki tai: Cyclone-driven suspended sediment effects on early benthic juvenile kōura (Jasus edwardsii), Te Ākau o Tokomaru, Aotearoa

authors: Karaha-Paki, Vijuan

abstract: Kōura (Jasus edwardsii) are ecologically, culturally, and economically significant taonga species central to mahinga kai systems throughout Aotearoa New Zealand. In Te Tairāwhiti, particularly Te Ākau o Tokomaru, Cyclone Gabrielle (February 2023) resulted in unprecedented sediment loads being delivered to coastal waters, smothering inshore rocky reefs that serve as critical nursery habitats for settling puerulus and juvenile kōura. This research investigated how repeated suspended sediment exposure affects the body condition, survival, and physiological condition of early benthic juvenile kōura, integrating Western scientific methods with mātauranga Māori perspectives to support kaitiakitanga and ecosystem recovery. 

A 52-day pulse-based laboratory experiment exposed 81 early benthic juvenile kōura to three treatment levels: Control (0 mg/L), Tobserved (1,000 mg/L), and Tmaximised (5,000 mg/L) suspended sediment concentrations, alternating between exposure phases and recovery periods to simulate natural post-storm sedimentation dynamics. Sediment was sourced from the Mangahauini River mouth to reflect local conditions. Kōura were initially housed communally (Days 1-19), and then separated into individual tāruke following observed cannibalism. Across the experiment, body weight to carapace length (BW:CL) ratios, survival, blood refractive index, gill condition, and moult stage were assessed. 

All treatment groups began with statistically equivalent body condition (p = 0.135), but cumulative effects emerged over time. During communal housing, mortality was highest in the Tobserved treatment (51.9%) compared with Control and Tmaximised treatments (both 18.5%). After separation, Tmaximised individuals showed the greatest losses (45.5%), mostly during the recovery rather than exposure phases. Overall mortality reached 45.7%, with sediment-exposed treatments experiencing 55% (Tmaximised) to 59% (Tobserved) losses compared with 22.2% in the Controls (p = 0.001). 

By Day 52, sediment exposure significantly reduced body condition (p = 0.016), with the Controls maintaining higher BW:CL ratios than Tmaximised (p = 0.013). Gill assessments indicated universal and severe damage in sediment-exposed kōura (100%) but none in the Controls (0%). Quantitative image analysis confirmed strong sediment concentration- dependent effects across all damage metrics – particle lodgement, filament integrity, surface discolouration, and composite scores (all p < 0.001) – with structural deformities in 66.7% of Tobserved and 100% of Tmaximised individuals. Blood refractive index showed no treatment differences, and 84.1% of kōura remained in intermoult stage at Day 52, with no significant difference in moult stage distribution between treatments (p = 0.328). However, moult frequency during the individual phase was lower in sediment-exposed groups compared to the Controls (Control: n = 11, Tobserved: n = 4, Tmaximised: n = 5). 

These findings show that suspended sediment exposure poses population-level threats to kōura recruitment through irreversible gill damage and delayed mortality. Elevated cannibalism during communal holding, particularly observed in the Tobserved treatment, likely resulted from temporal clustering of moult events rather than sediment-induced behaviour. For Te Ākau o Tokomaru and the wider CRA 3 fishery, this highlights the need for integrated catchment-to- coast management addressing land-derived sediment inputs and protecting coastal nursery habitats. From a Te Ao Māori perspective, sedimentation represents a disruption to whakapapa relationships with Tangaroa and a weakening of mauri in coastal ecosystems. Restoring these connections requires co-governance frameworks that embed mātauranga Māori, empower kaitiaki-led monitoring and rāhui, and address the cumulative impacts of land-use intensification and repeated cyclone events on ecosystem resilience in Te Tairāwhiti.

text: Mai uta ki tai: Cyclone-driven suspended sediment effects on early benthic juvenile kōura (Jasus edwardsii), Te Ākau o Tokomaru, Aotearoa Kōura (Jasus edwardsii) are ecologically, culturally, and economically significant taonga species central to mahinga kai systems throughout Aotearoa New Zealand. In Te Tairāwhiti, particularly Te Ākau o Tokomaru, Cyclone Gabrielle (February 2023) resulted in unprecedented sediment loads being delivered to coastal waters, smothering inshore rocky reefs that serve as critical nursery habitats for settling puerulus and juvenile kōura. This research investigated how repeated suspended sediment exposure affects the body condition, survival, and physiological condition of early benthic juvenile kōura, integrating Western scientific methods with mātauranga Māori perspectives to support kaitiakitanga and ecosystem recovery. 

A 52-day pulse-based laboratory experiment exposed 81 early benthic juvenile kōura to three treatment levels: Control (0 mg/L), Tobserved (1,000 mg/L), and Tmaximised (5,000 mg/L) suspended sediment concentrations, alternating between exposure phases and recovery periods to simulate natural post-storm sedimentation dynamics. Sediment was sourced from the Mangahauini River mouth to reflect local conditions. Kōura were initially housed communally (Days 1-19), and then separated into individual tāruke following observed cannibalism. Across the experiment, body weight to carapace length (BW:CL) ratios, survival, blood refractive index, gill condition, and moult stage were assessed. 

All treatment groups began with statistically equivalent body condition (p = 0.135), but cumulative effects emerged over time. During communal housing, mortality was highest in the Tobserved treatment (51.9%) compared with Control and Tmaximised treatments (both 18.5%). After separation, Tmaximised individuals showed the greatest losses (45.5%), mostly during the recovery rather than exposure phases. Overall mortality reached 45.7%, with sediment-exposed treatments experiencing 55% (Tmaximised) to 59% (Tobserved) losses compared with 22.2% in the Controls (p = 0.001). 

By Day 52, sediment exposure significantly reduced body condition (p = 0.016), with the Controls maintaining higher BW:CL ratios than Tmaximised (p = 0.013). Gill assessments indicated universal and severe damage in sediment-exposed kōura (100%) but none in the Controls (0%). Quantitative image analysis confirmed strong sediment concentration- dependent effects across all damage metrics – particle lodgement, filament integrity, surface discolouration, and composite scores (all p < 0.001) – with structural deformities in 66.7% of Tobserved and 100% of Tmaximised individuals. Blood refractive index showed no treatment differences, and 84.1% of kōura remained in intermoult stage at Day 52, with no significant difference in moult stage distribution between treatments (p = 0.328). However, moult frequency during the individual phase was lower in sediment-exposed groups compared to the Controls (Control: n = 11, Tobserved: n = 4, Tmaximised: n = 5). 

These findings show that suspended sediment exposure poses population-level threats to kōura recruitment through irreversible gill damage and delayed mortality. Elevated cannibalism during communal holding, particularly observed in the Tobserved treatment, likely resulted from temporal clustering of moult events rather than sediment-induced behaviour. For Te Ākau o Tokomaru and the wider CRA 3 fishery, this highlights the need for integrated catchment-to- coast management addressing land-derived sediment inputs and protecting coastal nursery habitats. From a Te Ao Māori perspective, sedimentation represents a disruption to whakapapa relationships with Tangaroa and a weakening of mauri in coastal ecosystems. Restoring these connections requires co-governance frameworks that embed mātauranga Māori, empower kaitiaki-led monitoring and rāhui, and address the cumulative impacts of land-use intensification and repeated cyclone events on ecosystem resilience in Te Tairāwhiti.

year: 2025