title: Relationships among male size, reproductive success, female choice and male advertising calls in Little Penguins (Eudyptula minor)

authors: Miyazaki, Masamine

abstract: The role of male acoustic features in the process of mate choice was investigated in Little Penguins (Eudyptula minor). Male call features and the calling behaviour may reveal important information on male attributes that could affect female choice. Larger males showed more aggressive behaviour to simulated nest intruders than smaller males. Chicks of larger males also grew at a faster rate than those of smaller ones, possibly because of differences in the quality of food delivered to chicks or paternal genetic effects on chick growth. However, there were no differences in fledging age, mass or success between larger and smaller males. Larger males also appeared to occupy or select better nest site; they occupied low and middle elevation nesting sites in comparison to smaller males, probably because the sites reduce energetic costs of walking on land. Larger males also mated earlier in the breeding season than smaller ones, suggesting that females may prefer larger males. Thus, male body size may play an important role in the attraction of potential mates in Little Penguins. Acoustic signals can influence female responses to males particularly in nocturnal seabirds. Larger males were found to produce lower-pitched call elements in their exhalation phrases than smaller males. In playback experiments with two loudspeakers, females did not distinguish low from high-pitched calls, although they responded vocally only to low-pitched calls. In another experiment, using current mate and stranger calls, females were more likely to approach their partners’ call and responded vocally only to their current partners, regardless of the stranger’s call pitch and, therefore, apparent size. Females may recognise their partners’ call and maintain mate fidelity even when larger, potentially more successful, strangers are presented. In addition to the effect of call pitch, calling patterns of males could influence female choice. By conducting experiments with a dual-speaker design in which calls from one speaker consistently overlapped those from the other speaker, I found that females approached overlapping advertising calls more than overlapped calls or a silent control speaker. The ‘masking effects’ of call overlap may obscure information that females require for mate choice. Alternatively, females may simply be able to locate overlapping calls more easily. It is possible that call overlap is associated with dominance or other quality indicators of the callers; thus, females may approach overlappers more often because they represent higher quality mates. My results indicate that acoustic signals can reflect the qualities of the males and that female Little Penguins may prefer larger males to enhance their reproductive potential.

text: Relationships among male size, reproductive success, female choice and male advertising calls in Little Penguins (Eudyptula minor) The role of male acoustic features in the process of mate choice was investigated in Little Penguins (Eudyptula minor). Male call features and the calling behaviour may reveal important information on male attributes that could affect female choice. Larger males showed more aggressive behaviour to simulated nest intruders than smaller males. Chicks of larger males also grew at a faster rate than those of smaller ones, possibly because of differences in the quality of food delivered to chicks or paternal genetic effects on chick growth. However, there were no differences in fledging age, mass or success between larger and smaller males. Larger males also appeared to occupy or select better nest site; they occupied low and middle elevation nesting sites in comparison to smaller males, probably because the sites reduce energetic costs of walking on land. Larger males also mated earlier in the breeding season than smaller ones, suggesting that females may prefer larger males. Thus, male body size may play an important role in the attraction of potential mates in Little Penguins. Acoustic signals can influence female responses to males particularly in nocturnal seabirds. Larger males were found to produce lower-pitched call elements in their exhalation phrases than smaller males. In playback experiments with two loudspeakers, females did not distinguish low from high-pitched calls, although they responded vocally only to low-pitched calls. In another experiment, using current mate and stranger calls, females were more likely to approach their partners’ call and responded vocally only to their current partners, regardless of the stranger’s call pitch and, therefore, apparent size. Females may recognise their partners’ call and maintain mate fidelity even when larger, potentially more successful, strangers are presented. In addition to the effect of call pitch, calling patterns of males could influence female choice. By conducting experiments with a dual-speaker design in which calls from one speaker consistently overlapped those from the other speaker, I found that females approached overlapping advertising calls more than overlapped calls or a silent control speaker. The ‘masking effects’ of call overlap may obscure information that females require for mate choice. Alternatively, females may simply be able to locate overlapping calls more easily. It is possible that call overlap is associated with dominance or other quality indicators of the callers; thus, females may approach overlappers more often because they represent higher quality mates. My results indicate that acoustic signals can reflect the qualities of the males and that female Little Penguins may prefer larger males to enhance their reproductive potential.

year: 2002

title: Predicting site productivity drivers for Podocarpus totara and modelling its growth with 3-PG

authors: Wade, Ashley Victoria

subjects: Forest modelling

abstract: Forests have been identified as key mitigation strategies to reduce net greenhouse gas emissions as they sequester and store carbon through growth. The Emissions Trading Scheme (ETS) and One Billion Tree (OBT) programme aim to increase tree plantings to offset these emissions by identifying exotic and indigenous tree species suitable for carbon sequestration across New Zealand. However, the rate of planting indigenous tree species has been slow as the species ability to sequester carbon is not well documented and legislation has prevented harvesting. The endemic conifer tōtara (Podocarpus totara D. Don) is an indigenous tree species which could be suitable for timber and carbon forestry. Previous studies have identified that tōtara can grow across a wide range of climatic and environmental conditions, however, few studies have investigated the key site productivity drivers and examined how they potentially influence productivity across sites. The aims of this study were to identify the main productivity drivers for tōtara across sites in the North Island of New Zealand and model growth using the 3-PG (Physiological Principles in Predicting Growth) forest growth model developed by Landsberg and Waring (1997). This study had two main hypotheses; 1) site fertility and temperature would be significant drivers of tōtara productivity and 2) the 3-PG growth model would be able to predict the growth of tōtara (stem diameter, basal area, volume, height and stand density) moderately well, providing a good fit to both the calibration and validation datasets with minimal error (RMSE). 

To test these hypotheses, 21 previously described planted and naturally regenerated tōtara stands across the North Island were selected. Fifteen sites were re-measured to investigate site productivity drivers for tōtara and to calibrate the 3-PG forest growth model. A multiple linear regression analysis using the backward elimination method was conducted to examine 22 growth related variables. Reineke’s (1933) stand density index (SDI) approach was used to identify trends in mortality as a function of stand density and size across sites. In addition, four volume equations by Ellis (1979), Coomes et al. (2002), Beets et al. (2012), and Todoroki and Steward (2019), that had previously been used to estimate volume of tōtara were tested to identify the most appropriate fit to two tōtara specific datasets. After model calibration, six additional sites, drawn from previous mensuration data were used to validate the model.  

The results from this study identified that climatic and soil physiochemical properties were significant drivers of tōtara productivity in planted and naturally regenerated stands. Temperature (max, mean and min), rainfall, elevation, soil total phosphorus, HCP ECa (horizontal coplanar receiver, apparent electromagnetic conductivity), and other soil macro and micronutrients (e.g. potassium and manganese) were selected as significant drivers of tōtara productivity from the multiple linear regression analysis; thus Hypothesis 1 of this study was supported. Currently, it is unclear how much these variables contribute to productivity and further research is recommended to investigate the level of contribution these significant drivers have on tōtara. Further investigation of more sites with collection of detailed growth and soil sampling data is recommended to develop a site fertility index for tōtara to quantify the role of fertility across sites. The volume equation developed by Todoroki and Steward (2019) provided the most appropriate fit to the tōtara dataset. A species-specific equation can therefore improve current estimates of volume in stands. In addition, the SDI index successfully identified relative stand densities for maximum and optimal stocking and can provide a basis for informing density management across tōtara sites. 

The 3-PG forest growth model predicted the growth of tōtara across sites with variable success. The 3-PG model provided reasonable estimates of stem diameter, height and stand density across the calibration sites (R2 ≥ 0.60 with low RMSE). However, the model consistently over-estimated basal area and volume. The model performed poorly (R2 ≤ 0.50) when tested with the validation dataset, and significantly over-estimated all growth variables apart from stand density. Therefore, the results did not support Hypothesis 2. This result could be due to the limited quantity and quality of data available and further investigation into the model’s parameters and algorithms is recommended. Overall, even though the results were less accurate than expected, they indicate that process-based models, like 3-PG, as opposed to empirical models, can be used to model species with limited datasets to identify base line information on growth over time and identify where additional research efforts should be directed to improve predictions.

This thesis emphasises the need to investigate a wider range of tōtara sites across varied soil fertility and productivity to improve the quality of the data available for growth modelling and forest management. This should include regular re-measurement of growth and long-term monitoring of climatic and edaphic factors across sites. This study has significantly improved the knowledge base available for tōtara to assist landowners, forest managers, iwi and the government to grow and manage tōtara for both commercial and non-commercial purposes.

text: Predicting site productivity drivers for Podocarpus totara and modelling its growth with 3-PG Forests have been identified as key mitigation strategies to reduce net greenhouse gas emissions as they sequester and store carbon through growth. The Emissions Trading Scheme (ETS) and One Billion Tree (OBT) programme aim to increase tree plantings to offset these emissions by identifying exotic and indigenous tree species suitable for carbon sequestration across New Zealand. However, the rate of planting indigenous tree species has been slow as the species ability to sequester carbon is not well documented and legislation has prevented harvesting. The endemic conifer tōtara (Podocarpus totara D. Don) is an indigenous tree species which could be suitable for timber and carbon forestry. Previous studies have identified that tōtara can grow across a wide range of climatic and environmental conditions, however, few studies have investigated the key site productivity drivers and examined how they potentially influence productivity across sites. The aims of this study were to identify the main productivity drivers for tōtara across sites in the North Island of New Zealand and model growth using the 3-PG (Physiological Principles in Predicting Growth) forest growth model developed by Landsberg and Waring (1997). This study had two main hypotheses; 1) site fertility and temperature would be significant drivers of tōtara productivity and 2) the 3-PG growth model would be able to predict the growth of tōtara (stem diameter, basal area, volume, height and stand density) moderately well, providing a good fit to both the calibration and validation datasets with minimal error (RMSE). 

To test these hypotheses, 21 previously described planted and naturally regenerated tōtara stands across the North Island were selected. Fifteen sites were re-measured to investigate site productivity drivers for tōtara and to calibrate the 3-PG forest growth model. A multiple linear regression analysis using the backward elimination method was conducted to examine 22 growth related variables. Reineke’s (1933) stand density index (SDI) approach was used to identify trends in mortality as a function of stand density and size across sites. In addition, four volume equations by Ellis (1979), Coomes et al. (2002), Beets et al. (2012), and Todoroki and Steward (2019), that had previously been used to estimate volume of tōtara were tested to identify the most appropriate fit to two tōtara specific datasets. After model calibration, six additional sites, drawn from previous mensuration data were used to validate the model.  

The results from this study identified that climatic and soil physiochemical properties were significant drivers of tōtara productivity in planted and naturally regenerated stands. Temperature (max, mean and min), rainfall, elevation, soil total phosphorus, HCP ECa (horizontal coplanar receiver, apparent electromagnetic conductivity), and other soil macro and micronutrients (e.g. potassium and manganese) were selected as significant drivers of tōtara productivity from the multiple linear regression analysis; thus Hypothesis 1 of this study was supported. Currently, it is unclear how much these variables contribute to productivity and further research is recommended to investigate the level of contribution these significant drivers have on tōtara. Further investigation of more sites with collection of detailed growth and soil sampling data is recommended to develop a site fertility index for tōtara to quantify the role of fertility across sites. The volume equation developed by Todoroki and Steward (2019) provided the most appropriate fit to the tōtara dataset. A species-specific equation can therefore improve current estimates of volume in stands. In addition, the SDI index successfully identified relative stand densities for maximum and optimal stocking and can provide a basis for informing density management across tōtara sites. 

The 3-PG forest growth model predicted the growth of tōtara across sites with variable success. The 3-PG model provided reasonable estimates of stem diameter, height and stand density across the calibration sites (R2 ≥ 0.60 with low RMSE). However, the model consistently over-estimated basal area and volume. The model performed poorly (R2 ≤ 0.50) when tested with the validation dataset, and significantly over-estimated all growth variables apart from stand density. Therefore, the results did not support Hypothesis 2. This result could be due to the limited quantity and quality of data available and further investigation into the model’s parameters and algorithms is recommended. Overall, even though the results were less accurate than expected, they indicate that process-based models, like 3-PG, as opposed to empirical models, can be used to model species with limited datasets to identify base line information on growth over time and identify where additional research efforts should be directed to improve predictions.

This thesis emphasises the need to investigate a wider range of tōtara sites across varied soil fertility and productivity to improve the quality of the data available for growth modelling and forest management. This should include regular re-measurement of growth and long-term monitoring of climatic and edaphic factors across sites. This study has significantly improved the knowledge base available for tōtara to assist landowners, forest managers, iwi and the government to grow and manage tōtara for both commercial and non-commercial purposes.

year: 2020

title: Coastal communities, leisure and wellbeing: Advancing a trans-disciplinary agenda for understanding ocean-human relationships in Aotearoa New Zealand

authors: Wheaton, Belinda

subjects: Science & Technology

abstract: Commentators are advocating for research to better understand relationships between healthy coastal ecosystems and human wellbeing. Doing so requires inter- and transdisciplinary approaches across humanities, arts, social sciences, and science and technology disciplines. These approaches include culturally diverse knowledge systems, such as indigenous ones, that locate sustainable use of and relationships to marine ecosystems. This paper contributes to this agenda through a case-study of relationships between coastal ecosystems and human wellbeing in Aotearoa New Zealand. This article highlights interconnected cultural and wellbeing benefits of, and socio-ecological relationships between, these coastal ecosystems drawing on a case study of one ocean-based, ‘immersive’ leisure activity, surfing. Further, it examines how these relationships impact human physical, emotional and spiritual wellbeing, and the wellbeing of communities and ecosystems. The research illustrates that surfing creates strong bonds between practitioners and coastal places, linking the health of marine environments and people. We demonstrate the value of a transdisciplinary place-based approach that integrates research across the humanities and social sciences and engages with Indigenous knowledge (Mātauranga Māori). This argument for multicultural co-learning shows the value of Western and Māori vantage points for how we understand coastal blue spaces. Indigenous perspectives, we conclude, deepen appreciation, as well as equity considerations, of how we understand place, wellbeing, and long-term sustainable relationships with marine ecosystems.

text: Coastal communities, leisure and wellbeing: Advancing a trans-disciplinary agenda for understanding ocean-human relationships in Aotearoa New Zealand Commentators are advocating for research to better understand relationships between healthy coastal ecosystems and human wellbeing. Doing so requires inter- and transdisciplinary approaches across humanities, arts, social sciences, and science and technology disciplines. These approaches include culturally diverse knowledge systems, such as indigenous ones, that locate sustainable use of and relationships to marine ecosystems. This paper contributes to this agenda through a case-study of relationships between coastal ecosystems and human wellbeing in Aotearoa New Zealand. This article highlights interconnected cultural and wellbeing benefits of, and socio-ecological relationships between, these coastal ecosystems drawing on a case study of one ocean-based, ‘immersive’ leisure activity, surfing. Further, it examines how these relationships impact human physical, emotional and spiritual wellbeing, and the wellbeing of communities and ecosystems. The research illustrates that surfing creates strong bonds between practitioners and coastal places, linking the health of marine environments and people. We demonstrate the value of a transdisciplinary place-based approach that integrates research across the humanities and social sciences and engages with Indigenous knowledge (Mātauranga Māori). This argument for multicultural co-learning shows the value of Western and Māori vantage points for how we understand coastal blue spaces. Indigenous perspectives, we conclude, deepen appreciation, as well as equity considerations, of how we understand place, wellbeing, and long-term sustainable relationships with marine ecosystems.

year: 2021