Behavioral Ecology and Parental Investment

Introduction

• Today's lecture focused solely on bird examples.

• Recap of previous lecture: Discussed social behavior and cooperation vs. conflict.

Natural Selection and Genes

• Natural selection operates at the gene level, not individual level.

• Importance of considering costs and benefits when analyzing behaviors.

• Core principle: Natural selection aims to increase reproductive success of genes.

Parent-Offspring Conflict

• Toy Example: Offspring demand more resources than parents are willing to provide.

  • Questions:

  • How much should offspring demand from parents?

  • How much should parents provide?

• Intuition suggests offspring should demand infinitely; however, reality differs.

• Provisioning Rates:

  • Let provisioning be denoted as p.

  • Increased resources improve offspring fitness but reduce resources available to parent.

• Natural Selection's Goal:

  • Maximize the difference between benefit and cost.

Genetic Perspective

• Offspring's gene controls resource demand, affecting its fitness.

• The gene's success depends on its presence in sibling offspring, with a relatedness coefficient of 0.5.

• Parent's gene controls resource provision, also with a relatedness of 0.5 affecting costs and benefits.

• The result is a formula: 0.5 imes ext{Benefit} - 0.5 imes ext{Cost} for both parent and offspring perspectives.

Graphical Representation

• Optimal provisioning from offspring perspective is higher than from parents, indicating a conflict.

Case Study: Stitched Bird

• Species: Threatened bird from New Zealand.

• Male and female provide resources to a single offspring.

• Without resource supplementation, unlikely to produce multiple broods.

• Experimental Setup:

  • Some parents and offspring supplemented with carotenoids.

  • Predictions:

  • Offspring with carotenoid supplementation should receive more food.

  • Parents supplemented should respond less to offspring's increased demand.

  • Result: Higher provisioning correlates with intensified begging signals from offspring.

Parental Investment in Evolutionary Context

• Examining which parents should provide care in monogamous breeding systems.

• Biparental Care: About 40 out of 100 studied shorebird species provide care from both parents.

• Cost vs. Benefit:

  • Benefits of remating vs. costs of current brood quality.

• Hypothesis: Higher male care predominates due to differing remating opportunities based on sex ratios.

Experiment on Parental Desertion

• Experimental Design:

  • Observation of survival rates when one parent is deserting.

  • Findings: Male desertion leads to significantly lower brood survival compared to female desertion.

  • Male survival rates lower when left unattended; shows higher associated costs.

Female Parenting Trends Through Breeding Season

• Graph of Hatching Dates vs. Female Care reveals that females tend to provide more care late in the breeding season.

• Brood Size Impact: Early in the season, larger broods receive more care; no impact in late season.

  • Cost of deserting increases with larger broods.

• Late-season females provide more care despite brood size, indicating that benefits of desertion are perceived to be lower at that time.

Conclusion

• Parent-offspring conflict and the varying ecological contexts can elucidate different behaviors.

• Conflict resolution relies heavily on understanding relative costs and benefits.

• Next Lecture Preview: Only one bird image guaranteed and more insights into patterns of behavior in animal systems.